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Time variations of streamwise positions of the shock waves shown in Fig. 11 (Configuration 8) and in Fig. 4c (Configuration 4)
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Presented are results from a parametric investigation of wind-tunnel test-section configurations with a goal of stabilization of normal-shock-wave structure. The test section includes a two-flow-passage arrangement, where each passage is separated by a shock-wave-holding plate. The top wall for the top passage is contoured relative to the streamwis...
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Ahmed Body is a standard and simplified shape of a road vehicle that's rear part has an important role in flow structure and it's drag force. In this paper flow control around the Ahmed body with the rear slant angle of 25° studied by using the plasma actuator system situated in middle of the rear slant surface. Experiments conducted in a wind tunn...
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... [11][12][13][14][15][16][17] For regular wind tunnels, the total pressure measured in the settling chamber or a value based on the estimation of the pressure loss can be approximated as the pressure after the valve, which in combination with the theoretical pressure regulation characteristics of the valve can be used to determine the displacement of the spool and to precisely regulate the total pressure through proportional integral differential (PID) closed-loop control. [18][19][20][21][22][23] In the testing process of the 2 m high-speed free jet wind tunnel in CARDC, the above method can cause problems such as prolonged flow field regulation, excessive pressure fluctuation, and even instability of the flow field. Therefore, a more precise prediction method is needed because (1) the wind tunnel has complex rectifier devices after the valve causing the pressure loss varies greatly under different pressure ratio, and therefore, the changes of pressure loss under different pressure ratio need to be considered; 24,25 (2) the pressure of the air source decreases rapidly when the flow rate is large, and the feedforward control of the pressure and valve position can be well executed only when the displacement of the spool is predicted more accurately; 15,19 and (3) under complex operating conditions such as continuous changes of the Mach number and pressure matching regulation, the pressure regulating valve must adjust the total pressure more quickly and accurately to meet the requirements of flow field establishment. ...
Prediction of the performance of the pressure-regulating valves in a large high-speed jet wind tunnel is important for obtaining and adjusting a high-quality flow field in the test section. In this work, we proposed a prediction method that corrects the theoretical characteristics of the pressure-regulation of the valve based on the experimental testing data of the ratio between the high- and low-pressure of the valve. The current method was validated for a given Mach number of 0.8, and the results showed that compared with the theoretical characteristics, the displacement deviation of the spool was reduced by 9.84%, and the total pressure deviation of the settling chamber was reduced by 43.61%. The results also show that compared with the single low-pressure ratio correction characteristic, the displacement deviation of the spool was reduced by 0.94%, and the total pressure deviation of the settling chamber was reduced by 3.4%. This method can consider the variation of the pressure loss for different pressure ratios and improve the pressure prediction of the valve.
... The position of the shock wave holding plate, which separates the two channels, and the choking flap, which chokes the flow in the bottom channel, were manipulated to position the shock wave and produce desired testing conditions. A similar test section approach was employed by Ligrani and Marko [24]. Also see Marko and Ligrani [25]. ...
Abstract Despite over fifty years of research on shock wave boundary layer effects and interactions, many related technical issues continue to be controversial and debated. The present survey provides an overview of the present state of knowledge on such effects and interactions, including discussions of: (i) general features of shock wave interactions, (ii) test section configurations for investigation of shock wave boundary layer interactions, (iii) origins and sources of unsteadiness associated with the interaction region, (iv) interactions which included thermal transport and convective heat transfer, and (v) shock wave interaction control investigations. Of particular interest are origins and sources of low-frequency, large-scale shock wave unsteadiness, flow physics of shock wave boundary layer interactions, and overall structure of different types of interactions. Information is also provided in regard to shock wave investigations, where heat transfer and thermal transport were important. Also considered are investigations of shock wave interaction control strategies, which overall, indicate that no single shock wave control strategy is available, which may be successfully applied to different shock wave arrangements, over a wide range of Mach numbers. Overall, the survey highlights the need for additional understanding of fundamental transport mechanisms, as related to shock waves, which are applicable to turbomachinery, aerospace, and aeronautical academic disciplines.
View Video Presentation: https://doi.org/10.2514/6.2021-3347.vid The UAH Propulsion Research Center (PRC) is in its 30th year at the University of Alabama in Huntsville (UAH). The mission of the Propulsion Research Center is to provide an environment that connects the academic research community with the needs and concerns of the propulsion community while promoting an interdisciplinary approach to solving propulsion problems. This paper summarizes recent metrics from academic and research programs. The emphasis this year is highlighting the production of close to 500 refereed publications over the past 30 years and highlighting the growth of the Mechanical and Aerospace Engineering program at UAH during that same time. The PRC continues to be a resource to perform both fundamental and applied research. It is also a significant contributor to workforce development in the propulsion and energy fields.
The present data illustrate a unique analysis approach to explore the physics of shock-wave-flow interactions, based upon correlation and spectral analysis of digitized shadowgraph visualization time-sequence data. As such, demonstration is provided of the use of high resolution, flow visualization data for quantitative correlation and spectral analysis. A shadowgraph system is employed to visualize time-varying, shock wave flow features within the test section of one leg of the transonic/supersonic wind tunnel (which is also referred to as the SS/TS/WT or SuperSonic/TranSonic/WindTunnel), located within the Propulsion Research Center of the University of Alabama in Huntsville. Of interest is a flow field with a well-defined normal shock wave, lambda foot, and separated turbulent boundary layer near the entrance of the lower flow passage (which is part of the test section), produced with a test section inlet Mach number of 1.54. Shadowgraph flow visualization images are processed from different pixel locations to compute frequency spectra. Data associated with two separate pixel region locations, each from a different flow region, are employed to determine magnitude squared coherence values, and associated time lag magnitudes. The data associated with lower Strouhal numbers in vicinity of 0.0013 and 0.0039 (which correspond to respective frequencies of 5 Hz and 15 Hz) illustrate important and pronounced interactions between the normal shock wave and the boundary layer separation zone. As this zone breathes and oscillates, additional flow locations are affected in a subsequent and significant manner. With Strouhal numbers in the vicinity of 0.0091, 0.0104, and 0.0260 (which correspond to respective frequencies of 35, 40, and 100 Hz), the most pronounced and significant interactions between the normal shock wave occur with respect to the downstream boundary layer. When Str equals 0.0091, spatially-varying time lag data show events with significant coherence propagate from a range of locations within the downstream boundary layer to the normal shock wave location. As such, events which originate within the downstream boundary layer at these experimental conditions are far more important (compared to events which originate with the upstream boundary layer) in regard to their effects on shock wave unsteadiness and associated flow motions.
The UAH Propulsion Research Center (PRC) is in its 29th year at the University of Alabama in Huntsville (UAH). The mission of the Propulsion Research Center is to provide an environment that connects the academic research community with the needs and concerns of the propulsion community while promoting an interdisciplinary approach to solving propulsion problems. This paper summarizes recent metrics from academic and research programs that are associated with the PRC. The emphasis this year is describing the graduate student production supported by the PRC over the past 29 years. This assessment identified over 270 theses and dissertations into 9 different propulsion categories. The results accumulated into 207 master’s and 67 Ph.D.s with the highest production rate being 21 degrees per year in 2010. The documents are distributed into categories representing conventional propulsion, advanced propulsion, missile design, air-breathing propulsion, Propulsion Testing, and Propulsion Systems Engineering. About 83% of the graduates are estimated to be U.S. citizens and there was a 20% female graduation rate. For the current year the total research expenditures from fifteen different agencies are anticipated to rise to $3.3 million which is a 33% compared to last year. PRC researchers published over 130 papers last year. The UAH student launch team placed 3rd in the NASA Student Launch national competition this year. The PRC continues to be a resource to accomplish high-quality research, education, and workforce development in propulsion and energy
