Measurements have been made of the growth by the Richtmyer-Meshkov instability of nominally single-scale perturbations on an air/sulfur hexafluoride ͑SF 6 ) interface in a large shock tube. An approximately sinusoidal shape is given to the interface by a wire mesh which supports a polymeric membrane separating the air from the SF 6 . A single shock wave incident on the interface induces motion by the baroclinic mechanism of vorticity generation. The visual thickness ␦ of the interface is measured from schlieren photographs obtained singly in each run and in high-speed motion pictures. Data are presented for ␦ at times considerably larger than previously reported, and they are tested for self-similarity including independence of initial conditions. Four different initial amplitude/wavelength combinations at one incident shock strength are used to determine the scaling of the data. It is found that the growth rate decreases rapidly with time, d␦/dtϰt Ϫp ͑i.e., ␦ ϰt 1Ϫp ), where 0.67ՇpՇ0.74 and that a small dependence on the initial wavelength 0 persists to large time. The larger value of the power law exponent agrees with the result of the late-time-decay similarity law of Huang and Leonard ͓Phys. Fluids 6, 3765-3775 ͑1994͔͒. The influence of the wire mesh and membrane on the mixing process is assessed.
CR contraction ratio (A t /A c ) h cIntake capture height L overall length of model m e mass flow rate at diffuser exit (kg/s) m i capture mass flow rate (kg/s) P static pressure P b back pressure P bs sustainable back pressure P i free stream pressure P 0e total pressure at exit P 0i total pressure of free stream PE pressure ratio at exit (P b /P i ) θ 1 first ramp angle θ 2 second ramp angle θ 3 first diffuser angle θ 4 second diffuser angle θ c cowl deflection angle x distance from leading edge Y distance along the height of intake Y max maximum intake exit height TH ratio of throttled area at exit and throat (A e /A t ) FD flow distortion PR pressure recovery ABSTRACT Experimental and computational investigations have been made to obtain the details of the flow field of a supersonic air-intake with different cowl deflection angles and back pressures at the exit. The flow field obtained with an inviscid computation on the basic configuration, designed for Mach 2·2, shows starting behaviour whereas computation with k-ω turbulence model and experiments indicate unstart characteristics. Both experiments and computations indicate that provision of a small angle at the cowl tip leads to start of the same intake and also improves it's performance. Results obtained with cowl deflection shows a better performance in comparison to performance achieved with a basic intake and with a bleed of 2·8%. Sustainable back pressure could be obtained through the computations made at different back pressures for different cowl deflection angles. Overall results suggest that provision of small cowl deflection angle itself leads to improvement in performance achieved in comparison to a bleed of 2·8%, even with back pressure at the exit.
NOMENCLATUREA t throat area A c capture area A e exit area
Experiments and computations have been made to obtain the details of the flow field over a slender body at high angles of attack at a freestream velocity of 17 m/s corresponding to a Reynolds number of 2.9×104based on the base diameter. Experiments indicated that the existence of side force at higher angles of attack is mainly due to the presence of asymmetric vortices in the leeward side. A rectangular cross-section circular ring placed at an axial distance of 3.5 times the base diameter reduced the side force at all the angles of attack. Investigations were made to obtain the effect of the height of the ring at an angle-of-attack of 50° where the side force experienced is relatively large. A ring placed at a distance of 3.5 times the base diameter alters the initial vortices and hence helps in substantial reduction of the side force. Studies with rings of different heights indicate that a ring having a height of 3% of the local diameter reduced the side force at almost all the angles of attack for the present flow conditions and provided the least disturbance to the lift and drag of the body.
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