The Effect of Pulsed Injection on Supersonic Shear Layer Mixing in a Scramjet Combustor

2018 ◽  
Vol 35 (3) ◽  
pp. 203-215
Author(s):  
Leslie Smith ◽  
Saeed Farokhi
Keyword(s):  
Wind Tunnel ◽  
Shear Layer ◽  
Test Section ◽  
Pulse Width ◽  
Static Pressure ◽  
Experimental Studies ◽  
Lower Wall ◽  
Supersonic Wind Tunnel ◽  
Scramjet Combustor ◽  
Secondary Injection

Abstract A novel injector has been designed and cold flow injection tests were performed in a modified supersonic wind tunnel. To complement these experimental studies three dimensional STAR-CCM+CFD simulations were developed. The pulse width may be varied, with options of injecting gas for 33 %, 50 % and 66 % of the injection period. The scramjet combustor environment is simulated in a supersonic wind tunnel through a backward facing step for secondary injection purposes and a 157.5 cm (62-inch) long test section. The gas in secondary injection is carbon dioxide and the primary flow is air. The simulations show a coupled interaction between the forcing from injection and the shear layer. Steady state static pressure measurements on the lower wall of the wind tunnel test section agree well with the simulated static pressure along the lower wall. The pulse width strongly impacts shear layer reattachment on the lower wall and varies between 2.4 and 4.3 step heights. Reduction in duty cycle from 66 % to 33 % at 1 kHz caused ~30 % reduction in the shear layer reattachments distance, which points to large scale mixing enhancement.

Experimental investigation of the effect of nozzle shape and test section perforation on the stationary and non-stationary characteristics of flow field in the large transonic TsAGI T-128 Wind tunnel

2005 ◽  
Vol 109 (1092) ◽  
pp. 75-82 ◽  
Author(s):  
V. I. Biryukov ◽  
S. A. Glazkov ◽  
A. R. Gorbushin ◽  
A. I. Ivanov ◽  
A. V. Semenov
Keyword(s):  
Wind Tunnel ◽  
Flow Field ◽  
Test Section ◽  
Static Pressure ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Experimental Investigations ◽  
Drive Power ◽  
Static Pressure Distribution ◽  
Nozzle Shape

Abstract The results are presented for a cycle of experimental investigations of flow field characteristics (static pressure distribution, static pressure fluctuations, upwash, boundary-layer parameters) in the perforated test section of the transonic TsAGI T-128 Wind Tunnel. The investigations concern the effect of nozzle shape, wall open-area ratio, Mach and Reynolds numbers on the above-outlined flow characteristics. During the tests, the main Wind-tunnel drive power is measured. Optimal parameters of the nozzle shape and test section perforation are obtained to minimise acoustic perturbations in the test section and their non-uniformity in frequency, static pressure field non-uniformity, nozzle and test section drag and, accordingly, required main Wind-tunnel drive power.

scholarly journals Optimizing the Coupling of a Firebrand Generator to a Horizontal Wind Tunnel

2013 ◽  
Vol 726-731 ◽  
pp. 971-976
Author(s):  
Javad Hashempour ◽  
Ahmad Sharifian
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Test Section ◽  
Experimental Studies ◽  
Fire Spread ◽  
Horizontal Wind ◽  
Experimental Facility ◽  
Velocity Difference ◽  
Wind Speeds ◽  
Computational Work

Australia is considered as the most fire-prone country in the world. Spotting ignition by lofted firebrands is the main mechanism of fire spread. Many experimental studies have been conducted to evaluate the effect of the firebrand attacks on structures and to identify possible solutions. The experimental facility consists of a firebrand generator coupled to a wind tunnel. The wind speed in the firebrand generator is relatively low, in order to assure a quality continuous flow of glowing firebrands. On the contrary, the wind speed in the wind tunnel is high to duplicate actual firebrand attacks. Previous works show a highly turbulent region above the entrance of firebrands to the wind tunnel which is formed because of the velocity difference and penetration of firebrand entrance hose into the wind tunnel. The penetration is required to provide a uniform firebrand distribution along the height of the test section. In this computational work, the influence of the height of the entrance hose, its orientation respect to the tunnel and the distance between the coupling port and the test section are analyzed. The optimized results are presented and discussed for a variety of wind speeds within the wind tunnel and the firebrand generator.

Design of Gust Wind Tunnel With Unsteady and Shear Main-Flows

2021 ◽  
Author(s):  
Yu Nishio ◽  
Ryotaro Miyazaki ◽  
Takanobu Ogawa
Keyword(s):  
Wind Tunnel ◽  
Shear Layer ◽  
Velocity Gradient ◽  
Test Section ◽  
Micro Air Vehicles ◽  
Strong Impact ◽  
Velocity Change ◽  
Linear Shear ◽  
Shutter Mechanism ◽  
Air Vehicles

Abstract Micro air vehicles (MAVs) have been developed for many fields. The MAVs usually receive strong impact from a velocity change in time or space, and facilities for aerodynamic experiments of MAVs under a gusty environment have been required. The present study has developed a gust wind tunnel to generate unsteady and non-uniform flows. We developed a small wind tunnel with eight multi-fans and a shutter mechanism at the upstream of the test section. We controlled the outputs of the fans independently and obtained a linear shear layer with an error of 5 percent. The velocity gradient of the shear layer was from 5 to 8 s−1. The shutter mechanisms provided a longitudinal gust with the velocity change from 2 m/s to 10 m/s within 0.3 seconds.

The Study of Design and Installation Process for Supersonic Nozzle

2012 ◽  
Vol 569 ◽  
pp. 500-503
Author(s):  
Lian Sheng Wu ◽  
Guang Li Li ◽  
Qi Fu
Keyword(s):  
Numerical Simulation ◽  
Wind Tunnel ◽  
Flow Field ◽  
Test Section ◽  
Supersonic Nozzle ◽  
Simulation Method ◽  
Supersonic Wind Tunnel ◽  
Numerical Simulation Method ◽  
Field Quality ◽  
The Impact

A practical optimal design method of supersonic nozzle is proposed for a supersonic wind tunnel’s design. Design a set of nozzle wall lines with the same nozzle length and different Mach numbers 1.5, 2.0, 2.5. Use numerical simulation method for the verify and analysis of the designed nozzle. Mainly study the impact of the installation gradient between nozzle and test section on flow field quality. This wind tunnel is the subsonic, transonic and supersonic wind tunnel and its test section cross is 0.2 m × 0.2 m .The impact on flow field quality of the test section was studied quantitatively by using the numerical simulation method. The installation gradient index was given. It has some practical value to the construction of supersonic wind tunnel. At present, this study has been applied in construction of the wind tunnel. The gradient of the test section import shall not be greater than 0.5 mm.

scholarly journals A Study of the Pulsations of Flow in the Settling Chamber and Their Relationship with the Pulsations of the Supersonic Flow

2019 ◽  
Vol 14 (2) ◽  
pp. 77-85
Author(s):  
L. V. Afanasev ◽  
A. A. Yatskih ◽  
A. D. Kosinov ◽  
Yu. G. Yermolaev ◽  
N. V. Semionov ◽  
...  
Keyword(s):  
Experimental Study ◽  
Supersonic Flow ◽  
Wind Tunnel ◽  
Test Section ◽  
Free Stream ◽  
Settling Chamber ◽  
Flow Pulsation ◽  
Supersonic Wind Tunnel ◽  
Flow Pulsations

Experimental study of the influence of flow pulsation in settling chamber on the supersonic free stream disturbances was carried out. Data on the pulsations in the settling chamber and the efficiency of deturbulization system as well as the correlation of pulsations of the flow of settling chamber and flow pulsations in test section of T-325 supersonic wind tunnel of ITAM SB RAS were obtained.

scholarly journals Measurementimprovement of flow quality of slotted test section in transonic wind tunnel

2021 ◽  
Vol 39 (3) ◽  
pp. 660-667
Author(s):  
Shenghao Wu ◽  
Jiming Chen ◽  
Qin Chen ◽  
Haitao Pei
Keyword(s):  
Mach Number ◽  
Wind Tunnel ◽  
Test Section ◽  
Experimental Studies ◽  
Flow Characteristics ◽  
Area Ratio ◽  
Straight Section ◽  
Flow Quality ◽  
Transonic Wind Tunnel

Experimental studies were carried out in the 0.6 m×0.6 m continuous transonic wind tunnel of CARDC in order to investigate the flow characteristics of the slotted test section. Experimental results show that the root-mean-square deviation of axial Mach number in the model area is above 0.01 when the test section Mach number is above 1.0.Numerical simulation under the same conditions to investigate the flow characteristics of the slotted section, together with the experimental studies indicate tow phenomena may directly cause the Mach number fluctuation. Firstly, a straight section was installed to connect the nozzle and the test section in the wind tunnel. Weak shock waves due to the curvature discontinuity at the joint of the test section and the straight section contribute to Mach number fluctuation. Secondly, the open-area ratio of both the upper and lower wall of test section, each with 8 slots, is of 10%. The larger porosity leads to stronger expansion waves in the acceleration zone located at the inlet of the test section. The flow was over accelerated because of the stronger expansion wave and thus fluctuate the flow field severely. Two measures were taken to improve the flow quality of the slotted test section based on the above-mentioned analysis: ①Flexible plate instead of solid straight plate was installed to bridge nozzle and test section to eliminate the curvature discontinuity; ②Decreasing the open-area ratio of the upper and lower test section wall to 6% and the number of slots to 6. Numerical and experimental results show that the Mach number fluctuation in the model area was suppressed to a satisfactory degree.

scholarly journals The Influence of Different Unsteady Incident Flow Environments on Drag Measurements in an Open Jet Wind Tunnel

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 178
Author(s):  
Xiao Fei ◽  
Christoph Jessing ◽  
Timo Kuthada ◽  
Jochen Wiedemann ◽  
Andreas Wagner
Keyword(s):  
Wind Tunnel ◽  
Unsteady Flow ◽  
Pressure Gradient ◽  
Test Section ◽  
Static Pressure ◽  
Signal Amplitude ◽  
Correction Method ◽  
Scale Model ◽  
Signal Frequency ◽  
On The Road

Aerodynamic development for road vehicles is usually carried out in a uniform steady-state flow environment, either in the wind tunnel or in Computational Fluid Dynamics (CFD) simulations. However, out on the road, the vehicle experiences unsteady flow with fluctuating angles of incidence β, caused by natural wind, roadside obstacles, or traffic. In order to simulate such flow fields, the Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart (FKFS) swing® system installed in the quarter scale model wind tunnel can create a variety of time-resolved signals with variable β. The static pressure gradient in the empty test section, as well as cD values of the Society of Automotive Engineers (SAE) body and the DrivAer model, have been measured under these transient conditions. The cD measurements have been corrected using the Two-Measurement Correction method in order to decouple the influence of the unsteady flow from that of the static pressure gradient. The investigation has determined that the static pressure gradient in the empty test section varies greatly with different excitation signals. Thus, it is imperative to apply a cD correction for unsteady wind tunnel measurements. The corrected cD values show that a higher signal amplitude, as in, signals with large β, lead to higher drag forces. The influence of the signal frequency on drag values varies depending on the vehicle geometry and needs to be investigated further in the future.

Analytical and Numerical Design of a High Performance Double–Throated Supersonic Blowdown Windtunnel

2016 ◽  
Author(s):  
Philipp Epple ◽  
Michael Steppert ◽  
Michael Steber
Keyword(s):  
Mach Number ◽  
Wind Tunnel ◽  
Design Process ◽  
Test Section ◽  
Method Of Characteristics ◽  
Design Procedure ◽  
Optimum Shape ◽  
Supersonic Wind Tunnel ◽  
Convergent Nozzle ◽  
The Method Of Characteristics

In this publication the focus lies on the design process of the full supersonic double throated wind tunnel. Starting with the fundamental equations of gas dynamics in combination with an analytical model of the pressure reservoir, the area of the throat at the nozzle and the runtime of the blowdown wind tunnel were computed. Based on these results, the shape of a shock free nozzle was calculated by the method of characteristics. For this purpose, a nozzle design program was developed using Python. In order to validate the results of the method of characteristics program, these results were compared with the area-Mach number relation, which is the exact analytical solution of the isentropic flow through supersonic nozzles. The convergent part of the nozzle, which initially accelerates the flow to sonic speed, cannot be calculated by the method of characteristics, since it applies to supersonic flows only. Hence the subsonic convergent section of the nozzle was designed directly with 2D CFD using CD Adapco Star-CCM+ v. 10.06. A parametric model of the convergent nozzle section was used to find the optimum nozzle shape, i.e. a nozzle which results in a maximum mass flow rate in order to have an undisturbed flow field and Mach number in the following test section. In order to decelerate the flow again from supersonic to subsonic flow after the test section and minimize the total pressure losses, an oblique shock diffuser was used [1]. As for the convergent subsonic nozzle, the optimum shape of a diffusor was found by 2D CFD analysis. Putting all these elements together, i.e. nozzle, test section and diffuser the optimum supersonic wind tunnel shape was found. Finally, a full 3D simulation of the supersonic wind tunnel was performed in order to validate the complete design procedure and computations and also to include the viscous effect of the side walls. These results and the whole design process are presented and analyzed in the paper.

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