Free Piston Shock Tunnels: A Survey

This report is an extension to an earlier study conducted at NAL concerning the development of a free piston shock tunnel. It has been demonstrated in the literature that Free Piston Shock Tunnels (FPST) can generate large stagnation, enthalpies of the order of 45 MJ/Kg [HEG] required for simulating realistic reentry aerodynamics. The report begins with a brief discussion on hypersonic flow regimes, simulation methodology and shortcomings of the conventional hypersonic testing facilities. The evolution of free piston tunnel from basic shock tube is presented in detail. An attempt is made to summarise the salient features and performance parameters of the existing and the new facilities planned elsewhere in the world. Some of the important operational problems associated with the existing facilities are also discussed

Supersonic testing of NAL binary pressure sensitive paint

The main objective of the present study is to subject NALPSP-02, an indigenously developed binary pressure sensitive paint, to supersonic flow conditions. An experimental study was carried out on a double-delta wing model at a free stream Mach number of 2.0 in the 0.3m trisonic wind tunnel at NAL. Pressure Sensitive Paint (PSP) technique was used to measure the pressure distribution on the lee side of the double delta wing at an incidences of 0°, 5°, 10° and 15°. The PSP results were compared against surface pressure data obtained using conventional pressure taps on the same model

Pressure-Sensitive Paint Measurements in a Blowdown Wind Tunnel

A methodology to correct for temperature effects on pressure-sensitive paint data in a blowdown wind tunnel has been suggested. PSP measurements using Optrod-B1 paint were made on an aircraft model instrumented with thermocouples and conventional pressure taps. The tests were made at freestream Mach numbers of 0.6 and 0.8 and at model incidences of 6 and 10 deg. The temperature correction is based on a mean model temperature concept for a given blowdown and the corrected PSP data are validated using pressure port data. It has been found that the accuracy of temperature-corrected PSP results is about as good as for those obtained at transonic speeds in other tunnels elsewhere

Pressure Sensitive Paint measurements in NAL 1.2m blowdown wind tunnel

A methodology to correct for the temperature effects of pressure sensitive paint data in a blowdown wind tunnel has been suggested. PSP measurements using Optrod-B1 paint were made on an aircraft model instrumented with thermocouples and conventional pressure taps. The tests were made at freestream Mach numbers of 0 .6 and 0.8 and at model incidences of 6° and 10°. The temperature correction is based on a mean model temperature concept for a given blowdown and the corrected PSP data is validated using pressure port data. It has been found that the accuracy of temperature corrected PSP results is as good as those obtained at transonic speeds in other tunnels elsewhere

NAL Binary PSP: Aging Tests at Transonic Speeds- part III

As a continuation, an experimental program to assess wind tunnel stability of binary pressure sensitive paint samples has been conducted in 0.3m tunnel on two newer paint formulations developed by Surface Engineering Division . This report summarises the details of these paints along with results

PSP Measurements on an Aircraft Wing-Body and Slenderbody Models in the NAL1.2m Trisonic Wind Tunnel.

This is the closure report submitted to the project sponsors AR&DB at the AR&DB project review meeting held on 03/5/2003 at DISC, Bangalore . An experimental study of PSP measurements was undertaken on aircraft and slenderbody models in the 1 .2m trisonic wind tunnel . A major objective of this programme was to provide a correction method of the drop in total temperature of the tunnel on PSP data and estimate accuracy of PSP measurements in a blowdown wind tunnel environment. Tests were made at Mach numbers of 0 .6 and-0 .8 at angle of attack of 6° and 100. A correction method for temperature effects on PSP data was evaluated and found very effective. The PSP results (using above correction method) showed very good agreement with pressure port data on the aircraft model . The accuracy of PSP results so obtained are considered to be about as good as those obtained in wind tunnels elsewhere in the world at transonic speeds

Shock-Wave Boundary-Layer Interaction Study on a 20' Compression Corner Using PSP and Kulites

An experimental unsteadiness in a mechanical vortex 12.56). study was conducted to control the separation shock Mach 2 20' compression ramp-induced interaction using generators (located upstream of interaction at 27.56 and Upstream of the interaction, traces of counter-rotating vortex pairs are clearly indicated by streamwise accumulation of oil pigment. These structures on interaction with the reverse flow in the separation bubble, replace a well-defined separation line (with no control case) by a corrugated separation line. The mean pressure distribution in the interaction region also gets modified and the corresponding rms distributions, in the intermittent region of separation, show a significant reduction in peak rms value. The VG configurations, therefore, help reduce the fluctuations of the separation shock and hence alleviate the fluctuating pressure loads in this region. Within the experimental limitations of transducer pitch and the extent of axial interaction, VG1 configuration seems to be a favorable control in both axial locations and hence seems to be a better flow control VG configuration

Shock-wave boundary-layer interaction study on a compression corner using pressure-sensitive paint

Experiments have been performed to study a compression corner induced turbulent boundary layer interactions in a freestream Mach number of 2.05 without and with control. Two configurations of vortex generators (VG), in the form of an array of delta ramps placed upstream of the interaction region at 27.5δ or h/δ = 0.65, have been tested to control the interaction. Pressure sensitive paint (PSP) measurements were made using a binary paint developed in-house. Reasonably good agreement of PSP results with mean static pressure measurements has been observed. The spanwise wall pressure distribution immediately downstream of the control devices show a sinusoidal pattern indicating the generation of streamwise vortices from VG devices. The interaction of these vortices with the reverse flow in the separated region replaced a well-defined separation line for no control by a highly corrugated separation line. Relative to the no-control case, the peak rms value in the intermittent region of separation with control showed significant modifications based on each VG configuration suggesting the effectiveness of VG devices in controlling the amplitude of shock oscillations in such interactions