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Experimental Investigation of Pressure Distribution in the Wind Tunnel Contarection and Preventation of Probable Separation
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor)
Abstract
Contraction sections are an integral part of all wind tunnels, whether designed for basic fluid flow research or model testing. The location of the contraction, just upstream of the test section, makes it very important to achieve a high quality contraction design. The effect of a contraction on unsteady velocity variations is significant to increase the mean velocity. Furthermore, contraction has a suitable role on the turbulence reduction in a wind tunnel. The contraction itself further reduces the turbulence in terms of percentage of the wind speed. This is due to the increase of the wind speed by a factor equal to the contraction ratio. In this research, to investigation flow quality in...
Control of pressure gradient in the contraction of a wind tunnel
, Article World Academy of Science, Engineering and Technology ; Volume 40 , 2009 , Pages 261-266 ; 2010376X (ISSN) ; Mirzaei, M ; Ghorbanian, K ; Sharif University of Technology
2009
Abstract
Subsonic wind tunnel experiments were conducted to study the effect of tripped boundary layer on the pressure distribution in the contraction region of the tunnel. Measurements were performed by installing trip strip at two different positions in the concave portion of the contraction. The results show that installation of the trip strips, have significant effects on both turbulence and pressure distribution. The reduction in the free stream turbulence and reduction of the wall static pressure distribution deferred signified with the location of the trip strip
Experimental study on correlation between turbulence and sound in a subsonic wind tunnel
, Article Acta Mechanica Sinica/Lixue Xuebao ; Volume 26, Issue 4 , 2010 , Pages 531-539 ; 05677718 (ISSN) ; Ghorbanian, K ; Soltani, M. R ; Sharif University of Technology
Abstract
In this paper, the effects of turbulence on sound generation and velocity fluctuations due to pressure waves in a large subsonic wind tunnel are studied. A trip strip located at different positions in the contraction part or at one position in the diffuser of a large wind tunnel is used to investigate the aforementioned phenomenon, and the results indicate that the trip strip has significant effects on sound reduction. The lowest turbulence intensity and sound are obtained from a trip strip with a diameter of 0.91mm located either at X/L = 0.79 or at X/L = 0.115 in the wide portion of the contraction. Furthermore, the effect of monopole, dipole and quad- rupole sources of aerodynamic noise...
Application of screens and trips in enhancement of flow characteristics in subsonic wind tunnels
, Article Scientia Iranica ; Volume 17, Issue 1 B , 2010 , Pages 1-12 ; 10263098 (ISSN) ; Ghorbanian, K ; Manshadi, M. D ; Sharif University of Technology
2010
Abstract
Subsonic wind tunnel experiments were conducted to study the turbulence level in the test section. Measurements were performed by introducing trip strip and/or damping screens on the flow field. The results indicated that the introduction of trip strips not only reduced the turbulence intensity compared to cases without it, but also flattened the variations. Further, the experiments which investigated the impact of the damping screens indicated a similar reduction in turbulence intensity; the pattern, however, remained the same. Furthermore, the results for cases wherein both trip strips as well as damping screens were placed on the contraction and in the settling chamber, respectively,...
Control of separation in the concave portion of contraction to improve the flow quality
, Article Aeronautical Journal ; Volume 113, Issue 1141 , 2009 , Pages 177-182 ; 00019240 (ISSN) ; Soltani, M.R ; Manshadi, M.D ; Mirzaei, M ; Sharif University of Technology
2009
Abstract
Subsonic wind tunnel experiments were conducted to study the effect of forced transition on the pressure distribution in the concave portion of contraction. Further more, the effect of early transition on the turbulence level in the test section of the wind tunnel is studied. Measurements were performed by installing several trip strips at two different positions in the concave portion of the contraction. The results show that installation of the trip strips, have significant effects on both turbulence intensity and on the pressure distribution. The reduction in the free stream turbulence as well as the wall static pressure distribution varied significantly with the location of the trip...
Power spectrum and FFT-based signal analysis in turbulence measurements
, Article World Academy of Science, Engineering and Technology ; Volume 40 , 2009 , Pages 275-278 ; 2010376X (ISSN) ; Tamadonfar, P ; Soltani, M. R ; Ghorbanian, K ; Masdari, M ; Sharif University of Technology
2009
Abstract
In this research, the employment of an innovative but simple and cost effective method for turbulent reduction in a low speed wind tunnel is investigated and the effect of this turbulence reduction on the Power Spectrum and FFT-Based signals that obtained from Hot-wire Anemometry is studied. These terms represents the amount of power contained in the signals. Several situations are studied in this paper. One of these situations is when there are four screens in the settling chamber of the wind tunnel and after that by adding the trip strip in the contraction region of the wind tunnel the tests were repeated. In the next stage, three screens were removed from the settling chamber of the wind...