Assessment of various low-profile mechanical vortex generators in controlling a shock-induced separation

An experimental investigation was conducted to assess the effectiveness of five microvortex generator configurations in controlling an incident shock-induced separation associated with a 14 deg shock generator in a Mach 2.05 flow. The vortex generator configurations studied include the Ashill, Anderson, split-Anderson, trapezoidal, and ramp-vane designs. Each device height h spanned 30% of the local boundary-layer thickness d estimated just upstream of the separation for no control. An array of each control device configuration was implemented 10δ upstream of the separation location for no control. Additionally, one ramp-vane device with h/δ = 0.5 was also tested. Out of all the configurations tested, the ramp-vane device (h/δ = 0.5) shows the maximum downstream shift (21%) in separation location. This device and the split-Anderson configuration (h/δ = 0.3) both show a reduction in the maximum rms values by 26 and 24%, respectively. The study on ramp-vane devices (h/δ = 0.3, 0.5) further shows that the size of the split relative to the device height also seems to be an important parameter. For the ramp-vane devices (h/δ = 0.3, 0.5), a smaller intervane spacing of 1.7h (h/δ = 0.5) instead of 3h (h/δ = 0.3) shows a very effective control. From this perspective, providing a split size of 1h in split-Anderson device has also shown favorable result

Utilization of sodium montmorillonite clay for enhanced electrochemical sensing of amlodipine

Nanosize surface of sodium montmorillonite has been prepared via sonication and deposited on glassy carbon electrodes for use as working electrode in a highly sensitive electrochemical biosensor for the detection of trace amounts of the calcium channel blocking drug, amlodipine. The cyclic voltammetric behaviour of amlodipine is studied in the pH range of 1.0−13.0. In alkali medium (pH 13.0) the sensor shows good response. Cyclic voltammograms show one oxidation peak and one broad reduction peak, which may be due to the oxidation of secondary amino group and reduction of chlorine and nitro groups respectively. Plots of log peak current and potential when correlated with log scan rate, indicate irreversible electron diffusion controlled redox reaction. The optimum conditions have been established by differential pulse stripping voltammetry. The anodic peak current is linear with concentration of the analyte at optimum conditions; the detection limit has been determined to be 0.01 mg/mL. A simple, sensitive and time-saving differential pulse stripping voltammetric procedure has been developed for estimation of amlodipine in its formulations as tablets

Evaluation of aerodynamic performance of sidewall compression intake relevant to air breathing propulsion vehicles for intake flow entry at M = 3.5

Wind tunnel studies were carried out on a 1:8.5 scale of side wall compression intake configuration model at free stream Mach number of 3.5. Starting characteristics of the intake was ascertained through wall pressure distribution and flow visualization pictures. The model has a convergent section, a nearly constant area section and divergent section, followed by a mass flow meter with a variable rear flap. Sidewalls with different leading edge sweeps of 30 and 45 degrees have been tested. Effect of sweep on mass flow has been studied for all cowl lengths. Pressure recovery is obtained for maximum cowl length. Results show sidewall sweep and the cowl length affect the mass flow entering the intake; and the maximum mass flow is seen with 30F sweep and the maximum range of mass flow is seen with differential sweep for a minimum cowl length

Study of Shock-Wave Boundary-Layer Interaction Control Using an Array of Steady Micro-Jet Actuators

An experimental investigation was conducted to control the amplitude of shock unsteadiness associated with the interaction induced by a (i) 24o compression corner and, (ii) a cylindrical obstruction on a flat plate in a Mach 2 flow. The control was applied in the form of an array of steady micro air-jets of different configurations with variation in pitch angle (β) and skew angle (α) of the jets. The overall flow interaction gets modified for all control configurations and shows a reduction in both separation- and bow-shock strengths and in triple-point height. A significant reduction in σmax /Pw value is also observed in the intermittent region of separation for each case. On the other hand, pitching or skewing the jets to 45o or both reduces the obstruction component considerably that initially, at lower control pressure, shows lower effectiveness (relative to 90o pitched jets). But at higher control pressure, the effectiveness of these configurations continues to increase unlike the 90o pitched jets

Shockwave/boundary-layer interaction control on a compression ramp using steady microjet

An experimental investigation was conducted to control the amplitude of shock unsteadiness associated with a 24 deg compression-ramp-induced interaction in a Mach 2 flow.Two control configurations in the form of an array of 1) 16 90-deg-pitched steady micro-air-jet vortex-generating devices (AJVG1), and 2) eight pairs of 45-deg-pitched steady micro-air-jet vortex-generating devices (AJVG2) were studied. EachAJVGdevice was placed upstream of the interaction region at 12:5� from the compression corner. Both micro-AJVG configurations show a reduction in separation shock strength and help considerably reduce the height of the lambda-wave triple point with increase in Poj . Pitching the microjets at 45 deg, as in the AJVG2 configuration, prevents a stronger control-generated bow shock to form ahead of the injectors and, hence, reduces the obstruction component of the interaction significantly. A well defined separation line for no control is seen to get replaced by a highly corrugated separation line with control. Significant reduction (up to 67%) in the peak rms value is observed in the intermittent region of separation with AJVG1 for Poj � 208:5 kPa while the same is achieved with AJVG2 at a much higher Poj�>500 kPa�. The spectral content of the pressure fluctuations also indicate that, relative to the AJVG2 configuration, AJVG1 is successful in reducing the amplitude of fluctuations in the range of unsteadiness by an order of magnitude as soon as Poj exceeds 208.5 kPa. The amplitude of these fluctuations is seen to further decrease with increase in Poj

Assessment of Flow Field Behind the Mechanical Vortex Generators at Mach 2.0

Experiments were carried out at M∞ = 2.05 to understand the flow development downstream of the mechanical vortex generators. Four control devices were tested, (i) rectangular vane, MVG1 (ii) ramp vane, MVG2 (iii) Anderson vane, MVG3 (iv) split-Anderson vane, MVG4. The total pressure values were obtained through two rakes (each consisting of 12 pitot tubes) placed along three streamwise locations of z = 5δ, 10δ and 15δ (where δ = 12.5 mm is the local boundary layer thickness for no-control). The velocity contour shows well-defined wake region behind that of all the control configurations. The wake appears to lift off from the plate surface with the increase in the streamwise distance. The relative velocity contour captures the momentum re-distribution occurring between the outer edge of boundary layer and the near-wall region. The oil flow visualization for control highlights the presence of vortex trails, which for MVG1 appears to be larger than other control configurations. The boundary layer profile along the vortex trails showed fullness to the profile for MVG1, whereas for MVG3-4, there is minimal change relative to that of the no-control

HSTDV Nozzle Contour Optimization for Enhanced Force Characteristics – Phase I

The SERN shape for the DRDL HSTDV program is a straight 2-D ramp (18 deg angle). It is known that a higher nozzle exit angle introduces divergence losses which can be reduced by properly contouring the nozzle so as to keep the nozzle exit angle as small as possible. Different nozzle design contour approaches were adopted. The force characteristics evaluated for each of these contours showed the 18 degree ramp to be better. The thrust optimized contour however resulted in a slight increase in CT relative to the 18degree ramp. But the CN value dropped significantly for this case

Separation and flow unsteadiness control in a compression corner induced interaction using mechanical vortex generators: Effects of vane size and inter-device spacing

An experimental investigation was conducted to control separation characteristics of a 24° compression corner induced interaction in a Mach 2.0 flow using an array of mechanical vortex generators (VGs) with rectangular vanes (RRV) placed 6.8δ upstream of the interaction. The objective was to study the effect of (i) inter-VG spacing (s/h = 12, 9.5, 8.0, 6.1, 5.7, 5.5, 4.9, and 4.7), (ii) vane chord length (c/h = 7.2, 4.2, and 3.0), and (iii) vane angle (α = 24°, 20°, 18°, and 16°) in controlling the interaction and on the surface flow topology. These modifications reduce the projected area of VGs in the array from the conventional VG design of RRV2 (c/h = 7.2 and s/h = 9.5) to RRV8 (c/h = 3.0 and s/h = 4.7) by 41%. Reducing s/h also reduces the inter-VG region of the separation significantly that helps to achieve maximum reduction in the streamwise extent of separation up to 83% and in the peak rms value up to 80%. The former improves the overall pressure recovery from 3.0 to 3.4, thereby moving closer toward the inviscid value of 3.8. Surface flow topology shows that the VG array splits a single large spanwise separation bubble for no control into multiple smaller scale individual separation cells placed side-by-side all along the span of the interaction. This helps to reduce the magnitude of mass exchange imbalance across each individual separation cell and, hence, stabilizes the overall interaction relative to no control. The best VG configuration of RRV8 shifts the dominant frequency of fluctuations to approximately 2 kHz or St = 0.19, which is nearly an order of magnitude higher than that for no control