Experimental Study of Two Impinging Jets Aligned With a Crossflow
ABSTRACT
Laser Doppler measurements provide information on the flowfield created by twin impinging jets aligned with a low velocity crossflow. The experiments were carried out for a Reynolds number based on the jet exit conditions of Rej = 4.3 × 104, an impingement height of 20.1 jet diameters and for a velocity ratio between the jet exit and the crossflow VR = Vj/Uo of 22.5, and an inter-jet spacing of S = 6D. The results show a large penetration of the first (upstream) jet that is deflected by the crossflow and impinges on the ground, giving rise to a ground vortex due to the collision of the radial wall and the crossflow that wraps around the impinging point like a scarf. The second jet (located downstream) is not so affected by the crossflow in terms of deflection, but due to the downstream wall jet that flows radially from the impinging point of the first jet it does not reach the ground. The results indicate a new flow pattern not yet reported so far, that is most relevant for a VSTOL aircraft operating in ground vicinity with front wind or small forward movement may result in enhanced under pressures in the aft part of the aircraft causing a suction down force and a change of the pitching moment towards the ground.
Laser Doppler measurements provide information on the flowfield created by twin impinging jets aligned with a low velocity crossflow. The experiments were carried out for a Reynolds number based on the jet exit conditions of Rej = 4.3 × 104, an impingement height of 20.1 jet diameters and for a velocity ratio between the jet exit and the crossflow VR = Vj/Uo of 22.5, and an inter-jet spacing of S = 6D. The results show a large penetration of the first (upstream) jet that is deflected by the crossflow and impinges on the ground, giving rise to a ground vortex due to the collision of the radial wall and the crossflow that wraps around the impinging point like a scarf. The second jet (located downstream) is not so affected by the crossflow in terms of deflection, but due to the downstream wall jet that flows radially from the impinging point of the first jet it does not reach the ground. The results indicate a new flow pattern not yet reported so far, that is most relevant for a VSTOL aircraft operating in ground vicinity with front wind or small forward movement may result in enhanced under pressures in the aft part of the aircraft causing a suction down force and a change of the pitching moment towards the ground.
Cite this paper
Barata, J. , Neves, F. , Vieira, D. and Silva, A. (2014) Experimental Study of Two Impinging Jets Aligned With a Crossflow. Journal of Modern Physics, 5, 1779-1788. doi: 10.4236/jmp.2014.516175.
Barata, J. , Neves, F. , Vieira, D. and Silva, A. (2014) Experimental Study of Two Impinging Jets Aligned With a Crossflow. Journal of Modern Physics, 5, 1779-1788. doi: 10.4236/jmp.2014.516175.
References
[1] Barata, J.M.M., Durao, D.F.G. and McGuirk, J. (1989) Journal of Aircraft, 26, 1002-1008.
http://dx.doi.org/10.2514/3.45873 [2] Knowles, K., and Bray, D. (1991) The Ground Vortex Formed by Impinging Jets in Crossflow. AIAA 29th Aerospace Sciences Meeting, Reno, 7-10 January 1991, AIAA Paper 91-0768. [3] Barata, J.M.M. (1989) Numerical and Experimental Study of Jets Impinging on Flat Surfaces through a Crossflow. Ph.D. Thesis, Instituto Superior Tecnico, Technical Univ. of Lisbon, Lisbon. (in Portuguese) [4] Sarippali, K.R. (1987) Laser Doppler Velocimeter Measurements in 3D Impinging Twin-Jet Fountain Flows. In: Durst, F., et al., Eds., Turbulent Shear Flows, Vol. 5, Springer-Verlag, Berlin, 147-168.
http://dx.doi.org/10.1007/978-3-642-71435-1_14 [5] Kind, R.J. and Suthanthiran, K. (1980) The Interaction of Two Opposing Plane Turbulent Wall Jets. AIAA Paper 72-0211, January. [6] Gilbert, B.L. (1983) Detailed Turbulence Measurements in a Two Opposing Plane Turbulent Wall Jets. AIAA 16th Fluid and Plasma Dynamics Conference, Danvers, 12-14 July 1983, AIAA Paper 83-1678. [7] Jenkins, R.C. and Hill Jr., W.G. (1977) Investigation of VTOL Upwash Flows Formed by Two Impinging Jets. Grumman Research Dept. Rept. RE-548, Bethpage, November. [8] Kotansky, D.R. and Glaze, L.W. (1980) The Effects of Ground Wall-Jet Characteristics on Fountain Upwash Flow Formation and Development. Report ONR-CR212-216-1F. [9] Kavasaoglu, M.S., Schetz, J.A. and Jakubowsky, A.K. (1989) Journal of Aircraft, 26, 793-804.
http://dx.doi.org/10.2514/3.45843 [10] Schetz, J.A., Jakubowsky, A.K. and Aoyagi, K. (1984) Journal of Aircraft, 21, 484-490.
http://dx.doi.org/10.2514/3.44997 [11] Araújo, S.R.B., Durao, D.F.G. and Firmino, F.J.G. (1981) Jets Impinging Normally and Obliquelly to a Wall. AGARD CP 308, Paper 5. [12] Sugiyama, Y. and Usami, Y. (1979) Bulletin of JSME, 22, 1736-1745. http://dx.doi.org/10.1299/jsme1958.22.1736 [13] Andreopoulos, J. and Rodi, W. (1984) Journal of Fluid Mechanics, 138, 93-127.
http://dx.doi.org/10.1017/S0022112084000057 [14] Shayesteh, M.V., Shabaka, I.M.N.A. and Bradshaw, P. (1985) Turbulent Structure of a Three-Dimensional Impinging Jet in a Crossflow. AIAA 23rd Aerospace Sciences Meeting, Reno, 14-17 January 1985, AIAA Paper 85-0044. [15] Kamotani, Y. and Greber, I. (1974) Experiments on Confined Turbulent Jets in a Crossflow. NASA CR-2392. [16] Stoy, R.C. and Ben-Haim, Y. (1973) Journal of Fluids Engineering, 95, 551-556. [17] Crabb, D., Durao, D.F.G. and Whitelaw, J.H. (1981) Journal of Fluids Engineering, 103, 142-153.
http://dx.doi.org/10.1115/1.3240764 [18] Barata, J.M.M., Durao, D.F.G. and McGuirk, J.J. (1989) Journal of Aircraft, 26, 1002-1008.
http://dx.doi.org/10.2514/3.45873 [19] Barata, J.M.M., Durao, D.F.G., Heitor, M.V. and McGuirk, J.J. (1993) Experiments in Fluids, 15, 117-129. [20] Barata, J.M.M. (1996) Ground Vortex Formation with Twin Impinging Jets. International Powered Lift Conference, Jupiter, 18-20 November 1996, Artigo SAE 962257. [21] Barata, J.M.M. (1996) AIAA Journal, 34, 2523-2530. [22] Metha R.D. and Bradshaw P. (1979) Design Rules for Small Low-Speed Wind Tunnels. The Aeronautical Journal of the Royal Aeronautical Society, November. [23] Durst, F., Melling, A. and Whitelaw, J.H. (1981) Principles and Practice of Laser-Doppler Anemometry. 2nd Edition, Academic Press, New York. [24] Yanta, W.J. and Smith, R.A. (1973) Measurements of Turbulent Transport Properties with a Laser-Doppler Velocimeter. 11th Aerospace Sciences Meeting, Washington DC, 10-12 January 1973. [25] Melling, A. and Whitelaw, J.H. (1975) Journal of Fluid Mechanics, 78, 285-315. [26] Baker, C.J. (1981) Journal of Wind Engineering and Industrial Aerodynamics, 6, 9-23.
http://dx.doi.org/10.1016/0167-6105(80)90018-5 [27] Saripalli, K.R. (1983) AIAA Journal, 21, 483-484.
http://dx.doi.org/10.2514/3.8102 [28] Siclari, M.J., Migdal, D., Luzzi Jr., T.W., Barche, J. and Palcza, J.L. (1976) Journal of Aircraft, 13, 938-944.
http://dx.doi.org/10.2514/3.58733 [29] Kotansky, D.R. (1981) The Modelling and Prediction of Multiple VTOL Aircraft Flow Fields in Ground Effect. AGARD CP-308, Paper 16.
[1] Barata, J.M.M., Durao, D.F.G. and McGuirk, J. (1989) Journal of Aircraft, 26, 1002-1008.
http://dx.doi.org/10.2514/3.45873 [2] Knowles, K., and Bray, D. (1991) The Ground Vortex Formed by Impinging Jets in Crossflow. AIAA 29th Aerospace Sciences Meeting, Reno, 7-10 January 1991, AIAA Paper 91-0768. [3] Barata, J.M.M. (1989) Numerical and Experimental Study of Jets Impinging on Flat Surfaces through a Crossflow. Ph.D. Thesis, Instituto Superior Tecnico, Technical Univ. of Lisbon, Lisbon. (in Portuguese) [4] Sarippali, K.R. (1987) Laser Doppler Velocimeter Measurements in 3D Impinging Twin-Jet Fountain Flows. In: Durst, F., et al., Eds., Turbulent Shear Flows, Vol. 5, Springer-Verlag, Berlin, 147-168.
http://dx.doi.org/10.1007/978-3-642-71435-1_14 [5] Kind, R.J. and Suthanthiran, K. (1980) The Interaction of Two Opposing Plane Turbulent Wall Jets. AIAA Paper 72-0211, January. [6] Gilbert, B.L. (1983) Detailed Turbulence Measurements in a Two Opposing Plane Turbulent Wall Jets. AIAA 16th Fluid and Plasma Dynamics Conference, Danvers, 12-14 July 1983, AIAA Paper 83-1678. [7] Jenkins, R.C. and Hill Jr., W.G. (1977) Investigation of VTOL Upwash Flows Formed by Two Impinging Jets. Grumman Research Dept. Rept. RE-548, Bethpage, November. [8] Kotansky, D.R. and Glaze, L.W. (1980) The Effects of Ground Wall-Jet Characteristics on Fountain Upwash Flow Formation and Development. Report ONR-CR212-216-1F. [9] Kavasaoglu, M.S., Schetz, J.A. and Jakubowsky, A.K. (1989) Journal of Aircraft, 26, 793-804.
http://dx.doi.org/10.2514/3.45843 [10] Schetz, J.A., Jakubowsky, A.K. and Aoyagi, K. (1984) Journal of Aircraft, 21, 484-490.
http://dx.doi.org/10.2514/3.44997 [11] Araújo, S.R.B., Durao, D.F.G. and Firmino, F.J.G. (1981) Jets Impinging Normally and Obliquelly to a Wall. AGARD CP 308, Paper 5. [12] Sugiyama, Y. and Usami, Y. (1979) Bulletin of JSME, 22, 1736-1745. http://dx.doi.org/10.1299/jsme1958.22.1736 [13] Andreopoulos, J. and Rodi, W. (1984) Journal of Fluid Mechanics, 138, 93-127.
http://dx.doi.org/10.1017/S0022112084000057 [14] Shayesteh, M.V., Shabaka, I.M.N.A. and Bradshaw, P. (1985) Turbulent Structure of a Three-Dimensional Impinging Jet in a Crossflow. AIAA 23rd Aerospace Sciences Meeting, Reno, 14-17 January 1985, AIAA Paper 85-0044. [15] Kamotani, Y. and Greber, I. (1974) Experiments on Confined Turbulent Jets in a Crossflow. NASA CR-2392. [16] Stoy, R.C. and Ben-Haim, Y. (1973) Journal of Fluids Engineering, 95, 551-556. [17] Crabb, D., Durao, D.F.G. and Whitelaw, J.H. (1981) Journal of Fluids Engineering, 103, 142-153.
http://dx.doi.org/10.1115/1.3240764 [18] Barata, J.M.M., Durao, D.F.G. and McGuirk, J.J. (1989) Journal of Aircraft, 26, 1002-1008.
http://dx.doi.org/10.2514/3.45873 [19] Barata, J.M.M., Durao, D.F.G., Heitor, M.V. and McGuirk, J.J. (1993) Experiments in Fluids, 15, 117-129. [20] Barata, J.M.M. (1996) Ground Vortex Formation with Twin Impinging Jets. International Powered Lift Conference, Jupiter, 18-20 November 1996, Artigo SAE 962257. [21] Barata, J.M.M. (1996) AIAA Journal, 34, 2523-2530. [22] Metha R.D. and Bradshaw P. (1979) Design Rules for Small Low-Speed Wind Tunnels. The Aeronautical Journal of the Royal Aeronautical Society, November. [23] Durst, F., Melling, A. and Whitelaw, J.H. (1981) Principles and Practice of Laser-Doppler Anemometry. 2nd Edition, Academic Press, New York. [24] Yanta, W.J. and Smith, R.A. (1973) Measurements of Turbulent Transport Properties with a Laser-Doppler Velocimeter. 11th Aerospace Sciences Meeting, Washington DC, 10-12 January 1973. [25] Melling, A. and Whitelaw, J.H. (1975) Journal of Fluid Mechanics, 78, 285-315. [26] Baker, C.J. (1981) Journal of Wind Engineering and Industrial Aerodynamics, 6, 9-23.
http://dx.doi.org/10.1016/0167-6105(80)90018-5 [27] Saripalli, K.R. (1983) AIAA Journal, 21, 483-484.
http://dx.doi.org/10.2514/3.8102 [28] Siclari, M.J., Migdal, D., Luzzi Jr., T.W., Barche, J. and Palcza, J.L. (1976) Journal of Aircraft, 13, 938-944.
http://dx.doi.org/10.2514/3.58733 [29] Kotansky, D.R. (1981) The Modelling and Prediction of Multiple VTOL Aircraft Flow Fields in Ground Effect. AGARD CP-308, Paper 16.