S. Raghunathan

Queen's University Belfast | QUB · School of Mechanical and Aerospace Engineeringu

Experiments were made on a two-dimensional low speed diffuser with passive control. The passive control consisted of porous surfaces made of holes/slots connected by a breather passage. Passive control postpones the stall and reduces buffet levels in the diffuser. This test confirms that passive controls to prevent flow separation are not restricte...

Passive control experiments were made on an 18% thick biconvex aerofoil model in Mach number range giving shock oscillations and at a Reynolds number of 0.7 x 10 ⁶ with fixed boundary layer transition. The control methods studied included a passive control of shock wave boundary layer interaction by a porous surface and a cavity, and a buffet breat...

Pressure fluctuation measurements were made on an 18% thick biconvex aerofoil in the region of shock boundary layer interaction at various levels of free stream flow unsteadiness. Experiments were performed with free transition and transition fixed models at a shock Mach number of 1.44 and blade chord Reynolds number of 1.6 x 10 ⁵ . The transition...

This paper investigates unsteady incompressible flow over cavities. Previous research in incompressible cavity-flow has included flow inside and past a 2-dimensional cavity, and flow inside a 3-dimensional cavity, driven by a moving lid. The present research is focused on incompressible flow past a 3-dimensional open shallow cavity. This involves t...

Variation of the bypass nozzle exit area enables optimization of the turbofan engine operating cycle over a wider range of operational conditions resulting in improved thrust and/or fuel consumption. Two mechanisms for varying the nozzle area have been investigated. The first uses an array of chevrons which when closed, form a full body of revoluti...

Transonic shock wave/boundary layer interaction over a wall-mounted bump was investigated with specific focus on shock wave unsteadiness and identification of its source. A large separation bubble resulted of an interaction driven by a flow characterized by a peak Mach number of 1.365. Overall this particular type of transonic unsteadiness is chara...

The paper focuses oil I lie, development of an aircraft design optimization methodology that models uncertainty and sensitivity analysis in the tradeoff between manufacturing cost, structural requirements and aircraft direct operating cost. Specifically rather than only looking at manufacturing cost, direct operating cost is also considered in term...

In this paper parametric analytical studies have been carried out for the geometrical optimization of dump diffusers for modern aero-gas turbine engines. Numerical studies have been carried out using SST K-Ω turbulence model. This code solves SST k-Ω turbulence equations using the coupled second order implicit unsteady formulation. In the numerical...

A study was conducted to investigate energy absorption and deformation in textile composite cellular structures (TCCS) under a quasi-static impact with various cell dimensions through 3-D finite element (FE) modeling. The aim of the study was to improve the absorption quality of TCCSs for various applications, especially for aerospace engineering,...

An experimental investigation of the effects of humidity-induced condensation on shock/boundary-layer interaction has been conducted in a transonic wind-tunnel test. The test geometry considered was a wall-mounted bump model inserted in the test section of the wind tunnel. The formation of a lambda-shape condensation shock wave was shown from schli...

There have not been any friction models applied to successfully predict distributions of contact stresses in flat rolling yet, in particular for the neutral plane. In this paper, the dynamic friction model (DFM) is expressed as a combination of both definitions of the viscosity and the friction, and is employed to derive underlying mathematical exp...

The studies undertaken have focused on engine nacelles, as being representative of the overall aircraft structure in terms of process technology and manufacturing-assembly philosophy. The aim of this project was to develop a cost-modelling methodology to highlight the optimum variance at which a manufacturing process should be maintained in order t...

Network communications transmit data as the foundation for the deployment of Net-Centric Operations (NCO). The data are transferred through a series of layers. These layers form the Architecture Reference Model (ARM). The applicability of several ARMs were presented and discussed. The ARMs can be classified to internet application, military/governm...

The development of the detrimental feature of intimal hyperplasia at the locations where bypass grafts are surgically attached to host arteries is believed to be promoted by haemodynamic factors. Thus, it is of interest to model the flow of blood through typical arterial bypass configurations in order to identify which features of the flow field en...

Data are presented on flow regimes, holdup and pressure drop for vertical co-current two phase flow in a 0.026 m i.d. pipe. A universal flow regime map was not possible but flow regime transitional equations were developed for the slug to churn, churn to semi-annular, semi-annular to annular and annular to annular ripple boundaries. Holdup was show...

Vertical three phase air-water-oil data in a. 0.026 m i.d. pipe were presented. The liquid holdup data presented as a complex pattern against f0 the oil liquid volumetric ratio for annular flow at one value of total superficial liquid velocity. The form of the pattern was explained in qualititive terms depending on the nature of the flow pattern pr...

The apparent differences between the momentum balance and energy balance derivation for the case of two-phase flow are resolved by examination of the liquid holdup within the system.

Theoretical studies have been carried out to examine internal flow choking in the inert simulators of a dual-thrust motor. Using a two-dimensional k-omega turbulence model, detailed parametric studies have been carried out to examine aerodynamic choking and the existence of a fluid throat at the transition region during the startup transient of dua...

In this paper, a combined experimental and numerical investigation of transonic shock wave/boundary layer interaction over a wall-mounted, circular-arc bump has been undertaken aiming to reveal information regarding the details of the flow and the capability of CFD in predicting such complex, yet fundamental, aerodynamic flows. CFD was first used i...

Aerodynamic sound reduction aims to ascertain ways for reducing aircraft noise to the point where it would be virtually imperceptible to normal human ears. Transonic buffeting appears more significant for silent aircraft design due to self-excited oscillation of shock waves. It is expected that transonic buffeting would also occur under gradually a...

An experimental investigation was carried out in order to study the fluid mechanics of pulsating transitional jets. The distance between the nozzle exit and the impinging plate was kept constant an equal to H=d = 3. The Reynolds number was also kept constant at approximately Re = 4200. Three pulsating frequencies were examined St ≈ 0:1; 0:25 and 0:...

The influence of even a single parameter change can be difficult to second guess at the design stage of a product. There may be many fluid, acoustic or structural performance effects that are sensitive to specific parameters. Modifiying the product to satisfy one area of performance may weaken it in others. The sensitivity of parameter changes in t...

Life cycle cost (LCC) is truly representative to the total cost of an aircraft through its life cycle. It is usually used for estimating the cost-effectiveness of an aircraft design. For enabling LCC estimation at early stage, A LCC model have been being developed for aircraft wing under the umbrella of Integrated Wing Advanced Technology Validatio...

Aluminium alloys are a series of traditional materials applied in aerospace industry. Composite materials have been being used to replace some aluminium alloys in airframe structures. To select a cost-efficient material in aerospace design, a framework for systematic assessment of composites and aluminium is therefore suggested. Through evaluation...

Simulations of the NASA Rotor 67, Stator 67A stage integrated into a bespoke nacelle were performed using ANSYS CFX. The throat area of the nacelle nozzle was varied by use of warped chevrons. 8, 12 and 16 chevron nozzles were simulated to evaluate the impact of the variation in geometry upon the nacelle wake and local forces. The force produced fr...

The current understanding of periodic transonic flow is reviewed briefly. The effects of boundary-layer transition, non-adiabatic wall conditions and modifications to the aerofoil surface geometry at the shock interactions on periodic transonic flow are discussed. Through the methods presented, it is proposed that the frequency of periodic motion c...

A methodology to estimate the cost implications of design decisions by integrating cost as a design parameter at an early design stage is presented. The model is developed on a hierarchical basis, the manufacturing cost of aircraft fuselage panels being analysed in this paper. The manufacturing cost modelling is original and relies on a genetic-cau...

The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, and aeroballistics, since it can create an extremely high-pressure state in a very short time. Of many different types of ballistic ranges developed to date, a two-stage light-gas gun is being employed mos...

The process of learning in any manufacturing enterprise contributes significantly to product lead times, final cost and ultimately, competitiveness. It effects all contributors to the product development cycle including individual operators and supervisors on the shop floor, as well as those involved in the upstream disciplines of engineering, tool...

Bias acoustic liners have been investigated by a number of researchers and demonstrated to have acoustic benefits. However while research has concentrated on the acoustic aspects of the liner, little research has directly investigated its heat transfer properties. A three dimensional numerical investigation of the fluid flow and heat transfer prope...

Multiple simulations of an isolated fan stage (NASA R67) were conducted using ANSYS CFX® with the Menter k-ω Shear Stress Transport turbulence model. After establishing suitable mesh densities for both rotor and stator domains, the simulations were extended to include surrounding nacelle geometries. The aim of this was to identify the optimal (bypa...

The work demonstrates the benefits of using digital methods for the development and optimization of large assembly manufacturing networks. Although an aircraft assembly has been used for this work, the methods and advontages of digital manufacturing techniques, which are demonstrated here, are equally applicable to any large assembly process, such...

Using a standard k-omega turbulence model the numerical studies have been carried out to examine the effect of transient temperature fluctuations and the boundary layer blockage on the internal flow features of solid rockets. This code solves standard k-omega turbulence equations with shear flow corrections using the coupled second order implicit u...

Efficient mass-bleed conditions to minimize base drag are examined in consideration of various base-to-orifice-exit area ratios for a body of revolution in the Mach 2.47 freestream. Axisymmetric, compressible, mass-averaged Navier-Stokes equations are solved using the standard kappa-omega turbulence model, a fully implicit finite volume scheme, and...

The paper is primarily concerned with the modelling of aircraft manufacturing cost. The aim is to establish an integrated life cycle balanced design process through a systems engineering approach to interdisciplinary analysis and control. The cost modelling is achieved using the genetic causal approach that enforces product family categorisation an...

The LHC magnet tests operation team developed various innovative techniques, particularly since early 2004, to complete the superconductor magnet tests by Feb. 2007. Overall and cryogenic priority handling, rapid on-bench thermal cycling, rule-based goodness evaluation on round-the-clock basis, multiple, mashed web systems are some of these techniq...

The work presented is concerned with the estimation of manufacturing cost at the concept design stage, when little technical information is readily available. The work focuses on the nose cowl sections of a wide range of engine nacelles built at Bombardier Aerospace Shorts of Belfast. A core methodology is presented that: defines manufacturing cost...

The mechanisms responsible for high ignition peak pressure, pressure rise rate, instabilities, and pressure oscillations observed during the static tests and the actual flight of certain class of high performance solid rocket motor (SRM) with nonuniform ports are discussed. A boundary layer growth is found to be occurring under the influence of the...

The internal flow choking and other design challenges associated with development of high-performance dual-thrust motors (DTM), because of their large size, high length to diameter ratio, and demanding thrust-time trace shape requirement, were discussed. At the subsonic inflow conditions, the occurrence of internal flow choking in DTMs was due to t...

Theoretical studies have been carried out to examine the internal flow choking in inert simulators of high-velocity transient (HVT) motors. Using a two-dimensional k-omega turbulence model, detailed parametric studies have been carried out to examine the aerodynamic choking and the existence of a fluid-throat, at the transition region, during the s...

The aim of the paper is to investigate numerically the effect of a DC positive corona discharge between two parallel wire electrodes of different diameter along an insulating aerofoil surface in low subsonic compressible flow. The modeling takes into account the two characteristic regions of the phenomenon: the corona sheath, surrounding the smalle...

The design of a cascade box within a cold stream thrust reverser is studied with a view to establishing a methodology for the optimization of aerodynamic, structural, manufacturing, and cost parameters. Aerodynamic and structural simulations have been carried out for three different design configurations. When the weight of the original cascade des...

The challenge in Aerospace Engineering, in the next two decades as set by Vision 2020, is to meet the targets of reduction of nitric oxide emission by 80%, carbon monoxide and carbon dioxide both by 50%, reduce noise by 50% and of course with reduced cost and improved safety. All this must be achieved with expected increase in capacity and demand....

Customer requirements and vision in aerospace dictate that the next generation of civil transport aircraft should have a strong emphasis on increased safety, reduced environmental impact and reduced cost without sacrificing performance. In this context, the School of Mechanical and Aerospace Engineering at the Queen's University of Belfast and Bomb...

The behavior of engineering systems arises as a direct result of interactions and interfaces between components. Whereas many of these intercomponent dependencies are easily identifiable, many others are obscure, often occurring as a res tilt of technical interactions between remote entities. The identification and management of system interactions...

The phenomena or mechanisms responsible for the ignition pressure spike, pressure rise rate, instabilities, and pressure oscillations often observed during the static tests and the actual flights of a certain class of dual-thrust motors (DTM) was studied. Inert simulators of solid rockets were selected to examine the occurrence of the internal flow...

The article presents cost modeling results from the application of the Genetic-Causal cost modeling principle. Industrial results from redesign are also presented to verify the opportunity for early concept cost optimization by using Genetic-Causal cost drivers to guide the conceptual design process for structural assemblies. The acquisition cost i...

A slip analysis has been developed to calculate the slip velocities from the capillary rheometry data for a polydimethylsiloxane (PDMS) gum, and two silicon rubber compounds. The analysis generalises the classical Mooney method [J. Rheol. 2 (1931) 210–222] to incorporate the influence of die geometry on the slip behaviour. For the PDMS gum, no slip...

The physics of the plume-induced shock and separation, particularly at high plume to exit pressure ratios with and without shock-turbulent boundary-layer control methods, were studied using computational techniques. Mass-averaged Navier-Stokes equations with a two-equation turbulence model were solved by using a fully implicit finite volume scheme...

Using a standard k-omega turbulence model, the influence of geometry-dependent driving forces on the formation of shock waves during the ignition transient of solid rocket motors have been examined. It was observed that, in addition to the igniter induced shock waves, at subsonic inflow conditions there is a possibility of the occurrence of shock w...

Using a standard k-ω turbulence model, in this paper detailed numerical computations have been carried out in inert simulators to examine the geometric dependence of transient flow features of solid rocket motors. We observed that the damping of the temperature fluctuation is faster in solid rocket with convergent port than with divergent port geom...

For technological reasons many high-performance solid rocket motors are made from segmented propellant grains with non-uniform port geometry. In this paper parametric studies have been carried out to examine the geometric dependence of transient flow features in solid rockets with non-uniform ports. Numerical computations have been carried out in a...

The School of Aeronautical Engineering at Queen's University Belfast, Northern Ireland collaborates with industrial and international establishments for imparting education and training in aerospace engineering. The school offers four-year MEng and three year BEng semesterized undergraduate degree programs covering the depth and width of aeronautic...

The effect of the turbulent transition on the onset of the transonic buffeting over the supercritical LV2F aerofoil is numerically investigated in the paper. The in-house RANS code validation has been done on 14% and 18% thick biconvex aerofoils as well as on the NACA0012 aerofoil. The importance in the results accuracy of both turbulence modelling...

In recent years, engine noise has been dramatically reduced and research on airframe noise reduction has attracted a growing attention. Various passive and active noise control technologies have been studied but there are few activities on integration of noise reduction techniques into aircraft design. The aim of this study is to pursue an avenue,...

Key component of an aircraft power plant system is the thrust reverser. The thrust reverser considered in this paper uses the natural blockage concept, with only the fan duct flow being reversed. This paper focuses on the study of the aerodynamic performance of the cascade within a cold stream thrust reverser. Aerodynamic simulations are carried ou...

The primary intention of this paper is to review the current state of the art in engineering cost modelling as applied to aerospace. This is a topic of current interest and in addressing the literature, the presented work also sets out some of the recognised definitions of cost that relate to the engineering domain. The paper does not attempt to ad...

This paper presents results of investigations of unsteady incompressible flow past three-dimensional cavities, where there is a complex interaction between the external flow and the recirculating flow inside the cavity. A computational fluid dynamics approach is used in the study. The simulation is based on the solution of the unsteady Navier-Stoke...

This paper focuses on the aerodynamic and structural design of the cascade within a cold stream thrust reverser. Methodologies are established for improving the efficiency of the design process. Aerodynamic and structural simulations are carried out using realistic operating conditions for idealized cascade models representing three design options....

Systems Engineering provides a set of methods and approaches that can be used to handle the interactions between different components and disciplines involved in a design process. This work demonstrates a framework that uses automation and analysis integration methods and allows for the automatic generation simulation models and results, which are...

The paper is concerned with the modelling of engineering driven costs for integration into a systems engineering approach. The methodology presents a Genetic Causal cost modelling concept that isolates product families and their causal relationship to engineering design parameters. This includes the initial modelling for each stage of assembly buil...

Aerospace companies and universities conduct strategic collaborative research projects, one of the aims of which is to transfer technology between the parties involved. However, barriers such as the difficulty of transferring tacit knowledge, the cultural differences between universities and companies, interpersonal difficulties and labour turnover...

SYNOPSIS The paper presents the effect of rotor geometry on the performance of a small-scale Wells turbine for wave energy conversion. In the study, four kinds of blade profile were selected from previous studies with regard to the blade profile of the Wells turbine. The types of blade profile included in the paper are as follows: NACA0020; NACA001...

Plume interference effects on the axisymmetric flowfields around powered missiles are investigated using computational techniques. The study is mainly to understand the physics of the plume-induced shock and separation particularly at high plume to exit pressure ratios with and without shock-turbulent boundary layer control methods. Mass-averaged N...

An experimental investigation was carried out to study the effect of flow pulsation frequency on the local and average heat transfer characteristics of a heated air jet. The experiments were performed for steady jets and for pulsating jets at frequencies from 10 to 80 Hz. The nozzle to plate spacing, x/D was fixed at 4 and Reynolds number was set a...

Major customer requirements and design drivers in aerospace are highlighted. Some of the current research activities at Queens University Belfast in meeting the customer requirements are presented. Key cost drivers were identified and a cost model was developed and validated. The cost model was used to develop methodologies for evaluation of the co...

1.0 Summary frequency, it is possible to make a 60% reduction in suitable cascade design concepts relatively early in the design process. This will represent a considerable time and cost saving when the design This paper focuses on design procedures for the cascade within a cold stream thrust reverser, see Figures 1 and 2. Levels of stress and disp...

Aerospace companies and universities conduct strategic collaborative research projects, one of the aims of which is to transfer technology between the involved parties. What is not found in the technology transfer literature is a practical model to guide the process. The aim of this research is to produce such a model along with an accompanying man...

Aircraft acquisition cost contribution to the direct operating cost is about three to four times higher than the contribution made by fuel cost for the sector of operation. As a result, commercial aircraft design is driven more by customer demands of reduced acquisition cost and lead-time than by technology itself. The paper describes the fabricati...

The influence of manufacturing tolerance on direct operating cost (DOC) is extrapolated from an engine nacelle to be representative of an entire aircraft body. Initial manufacturing tolerance data was obtained from the shop floor at Bombardier Aerospace Shorts, Belfast while the corresponding costs were calculated according to various recurring ele...

This paper summarises the experimental results of the research undertaken at the School of Aeronautical Engineering at the Queen’s University of Belfast regarding the effects of distributed roughness elements on two-dimensional turbulent boundary layers. All the experiments were conducted on a smooth flat plate model. Data was first collected for t...

Computational Fluid Dynamic studies were conducted for realistic missile configurations with and without the exhaust plume for a range of Mach numbers M = 0.8 to 4.0, a range of plume supply pressure 1.5 atms to 2000 atms and with several turbulence models. The code was validated for simple missile configurations. The test range covered both over e...

The adaptive wing concept of Contour Bumps is numerically investigated for drag reduction and extending the buffet boundary in transonic periodic flows. The periodic shock oscillations are initiated on a NACA0012 adapted aerofoil by moving the aerofoil from a regime of steady transonic flow into a regime of periodic flow by a change in airflow inci...

The concept modeling for aircraft manufacturing cost estimation was presented. The aircraft cost drivers were integrated through cost analysis to improve the competitive design and manufacturing of aircraft. The cost prediction models were developed to make more competitive decisions within the integrated design process.

The rimming flow of a power-law fluid in the inner surface of a horizontal rotating cylinder is investigated. Exploiting the liquid layer being thin the simplest lubrication theory is applied. The generalized run-off condition for the steady-state flow of the power-law liquid is derived. In the bounds implied by this condition film thickness admits...

The paper looks at current methods of aircraft design and manufacture, focusing on their inter-relationship and the resultant influence on product cost. After investigating detailed instances of aircraft manufacture and assembly, primarily with regards to cost, a methodology that integrates these is presented. The method is deployed to predict the...

Rimming flow of a liquid polymer on the inner surface of a horizontal rotating cylinder is investigated. Using a scale analysis, a theoretical description for steady-state non-Newtonian flow is obtained. Simple lubrication theory is applied since the Reynolds number is small and the liquid film thin. Since a steady-state viscometric flow is conside...

A variety of designs of self-rectifying air turbines for wave power conversion have been proposed over the last decade. However, the noise characteristics of the turbines have not been presented so far. In order to clarify the noise characteristics of the turbines, experimental investigations have been performed under steady flow conditions in this...

Up until now, aircraft surface smoothness requirements have been aerodynamically driven with tighter manufacturing tolerance to minimize drag, that is, the tighter the tolerance, the higher is the assembly cost in the process of manufacture. In the current status of commercial transport aircraft operation, it can be seen that the unit cost contribu...

A Wells turbine is one of the simplest and promising self-rectifying air turbines which is basic to the needs of the near future and likely to be economically viable. With the recent development in computer hardware and software, it has now become practicable to conduct a reasonable computation of three-dimensional turbulent flows through complex g...

Simple correlations for heat transfer on an attachment line in hypersonic flow are proposed as best fits to transitional and turbulent cases. A wide range of experimental results obtained in low enthalpy facilities, is used to sustain these models. It is observed that for long cylinders a nearly asymptotic state can be reached. Thus, transition Rey...

This paper reports the results of an experimental investigation into the effect of a wall normal vibration on a zero pressure gradient turbulent boundary layer over a flat plate (690mm * 200mm * 12mm). Tests were conducted in a subsonic wind tunnel at 17m/s. An electromagnetic shaker, in conjunction with a vibration control system was used to suppl...

The cost impact of aerodynamic tolerances on the wetted surface of an engine nacelle is considered. Manufacturing tolerance data were obtained from Bombardier Aerospace Shorts, Belfast, while the corresponding costs were calculated according to various recurring elements such as basic and overtime labour, rework, concessions, redeployment, etc., al...

Experimental investigations directed toward further understanding and improved prediction of heat transfer in an aircraft nacelle anti-icing system are presented. The results are correlated with existing predictions. A unique correlation based on the heat transfer impingement area is developed. The correlation is independent of the distance between...

An integrated multidisciplinary approach to aerospace design is presented as a means of improving the present state of the art towards a more effective concurrent methodology empowered by costing tools. Only the most influential drivers are identified and structured into a preliminary costing framework that supports decision making upfront in the d...

Rimming flow on the inner surface of a horizontal rotating cylinder is investigated. Using a scale analysis, a theoretical description is obtained for steady-state non-Newtonian flow. Simple lubrication theory is applied since the Reynolds number is small and liquid film thin. Since the Deborah number is very small the flow is viscometric. The Weis...

The rimming flow of apower-law fluid in the inner surface of ahorizontal rotating cylinder is investigated. Exploiting the fact that the liquid layer is thin, the simplest lubrication theory is applied. The generalized run-off condition for the steady-state flow of the power-law liquid is derived. In the bounds implied by this condition, film thick...

In order to investigate the effectiveness of an orifice system in producing pressure drops and the effect of compressibility on the pressure drop, computations using the mass-averaged implicit Navier-Stokes equations were applied to the axisymmetric pipe flows with the operating pressure ratio from 1.5 to 20.0. The standard k- ɛ turbulence model wa...

Rimming flow on the inner surface of a horizontal rotating cylinder is investigated. Using a scale analysis, a theoretical description is obtained for steady-state non-Newtonian flow. Simple lubrication theory is applied since the Reynolds number is small and liquid film thin. Since the Deborah number is very small the flow is viscometric. The Weis...

This paper investigates unsteady incompressible flow over cavities. Previous research in incompressible cavity flow has included flow inside and past a 2-D cavity, and flow inside a 3-D cavity, driven by a moving lid. The present research is focused on incompressible flow past a 3-D cavity. This involves the complex interaction between the external...

Critical reviews made by various organisations on both sides of the Atlantic have identified the need for continuing changes in engineering teaching curriculum, emphasising inclusion of more intense design education to meet the requirements of industry. The concept of this paper outlines introducing design education within aerospace engineering in...