scholarly journals Interaction of Wake and Propulsive Jet Flow of a Generic Space Launcher

2020 ◽  
pp. 129-143
Author(s):  
Alexander Barklage ◽  
Rolf Radespiel
Keyword(s):  
Pressure Ratio ◽  
Jet Flow ◽  
Main Body ◽  
Outer Flow ◽  
Passive Flow Control ◽  
Flow Control Devices ◽  
Flow Phenomena ◽  
Dual Bell ◽  
Propulsive Jet ◽  
Space Launcher

Abstract This work investigates the interaction of the afterbody flow with the propulsive jet flow on a generic space launcher equipped with two alternative nozzle concepts and different afterbody geometries. The flow phenomena are characterized by experimental measurements and numerical URANS and LES simulations. Investigations concern a configuration with a conventional truncated ideal contour nozzle and a configuration with an unconventional dual-bell nozzle. In order to attenuate the dynamic loads on the nozzle fairing, passive flow control devices at the base of the launcher main body are investigated on the configuration with TIC nozzle. The nozzle Reynolds number and the afterbody geometry are varied for the configuration with dual-bell nozzle. The results for integrated nozzles show a shift of the nozzle pressure ratio for transition from sea-level to altitude mode to significant lower levels. The afterbody geometry is varied including a reattaching and non-reattaching outer flow on the nozzle fairing. Investigations are performed at supersonic outer flow conditions with a Mach number of $$Ma_\infty =3$$. It turns out, that a reattachment of the outer flow on the nozzle fairing leads to an unstable nozzle operation.

scholarly journals Investigation of the base flow of a generic space launcher with dual-bell nozzle

2020 ◽  
Author(s):  
Sven Scharnowski ◽  
Christian J. Kähler
Keyword(s):  
Mach Number ◽  
Pressure Ratio ◽  
Base Flow ◽  
Nozzle Pressure Ratio ◽  
Flow Topology ◽  
Outer Flow ◽  
Separated Shear Layer ◽  
Nozzle Pressure ◽  
Dual Bell ◽  
Space Launcher

Abstract The typical afterbody flow of a space launcher is characterized by a strong interaction of the engine’s exhaust jet and the separated shear layer emerging from the main body. This interaction is further complicated by strong changes in the spatial and temporal behavior of the afterbody flow during the atmospheric ascent of a launcher. Theoretically, a dual-bell nozzle not only allows for a gain in payload compared to standard single-bell nozzles, but also it alters the wake flow topology due to the two nozzle modes. To predict the benefits as well as the additional risks, the afterbody flow of a generic space launcher model equipped with a cold-flow dual-bell nozzle is investigated in detail. The flow was analyzed for sub-, trans- and supersonic Mach numbers ranging from 0.3 to 2.9 for a variety of nozzle pressure ratios. Particle image velocimetry measurements and schlieren measurements with high repetition rate were performed to determine the dynamics of the separated shear layer, the nozzle jet and their interaction. It is shown that the reattachment length of the base flow decreases with increasing nozzle pressure ratio. Furthermore, the nozzle pressure ratio at which the dual-bell nozzle switches from sea-level mode to altitude mode is reduced by $$15\%$$ 15 % with high subsonic outer flow and by as much as $$65\%$$ 65 % for an outer flow at a Mach number of 1.6. Even for a constant nozzle pressure ratio, the nozzle flow topology depends on the Mach number of the outer flow.

scholarly journals Numerical Analysis of the Turbulent Wake for a Generic Space Launcher with a Dual-Bell Nozzle

2020 ◽  
pp. 163-177
Author(s):  
Simon Loosen ◽  
Matthias Meinke ◽  
Wolfgang Schröder
Keyword(s):  
Flow Control ◽  
Pressure Ratio ◽  
Low Frequency ◽  
Turbulent Wake ◽  
Dynamic Mode Decomposition ◽  
Time Resolved ◽  
Mode Decomposition ◽  
Spatio Temporal ◽  
Dual Bell ◽  
Space Launcher

Abstract The turbulent wake of an axisymmetric generic space launcher equipped with a dual-bell nozzle is simulated at transonic ($$Ma_\infty = 0.8$$ and $$Re_D = 4.3\cdot 10^5$$) and supersonic ($$Ma_\infty = 3$$ and $$Re_D = 1.2\cdot 10^6$$) freestream conditions, to investigate the influence of the dual-bell nozzle jet onto the wake flow and vice versa. In addition, flow control by means of four in circumferential direction equally distributed jets injecting air encountering the backflow in the recirculation region is utilized to determine if the coherence of the wake and consequently, the buffet loads can be reduced by flow control. The simulations are performed using a zonal RANS/LES approach. The time-resolved flow field data are analyzed by classical spectral analysis, two-point correlation analysis, and dynamic mode decomposition (DMD). At supersonic freestream conditions, the nozzle counter pressure is reduced by the expansion of the outer flow around the nozzle lip leading to a decreased transition nozzle pressure ratio. In the transonic configuration a spatio-temporal mode with an eigenvalue matching the characteristic buffet frequency of $$Sr_D=0.2$$ is extracted by the spectral and DMD analysis. The spatial shape of the detected mode describes an antisymmetric wave-like undulating motion of the shear layer inducing the low frequency dynamic buffet loads. By flow control this antisymmetric coherent motion is weakened leading to a reduction of the buffet loads on the nozzle fairing.

scholarly journals Numerical Analysis of Side-loads Reduction in a Sub-scale Dual-bell Rocket Nozzle

2021 ◽  
Author(s):  
M. Cimini ◽  
E. Martelli ◽  
M. Bernardini
Keyword(s):  
Inflection Point ◽  
Pressure Ratio ◽  
Mean Value ◽  
Detached Eddy Simulation ◽  
Turbulent Structures ◽  
Eddy Simulation ◽  
Separation Shock ◽  
Delayed Detached Eddy Simulation ◽  
Controlled Flow ◽  
Dual Bell

AbstractA calibrated delayed detached eddy simulation of a sub-scale cold-gas dual-bell nozzle flow at high Reynolds number and in sea-level mode is carried out at nozzle pressure ratio NPR = 45.7. In this regime the over-expanded flow exhibits a symmetric and controlled flow separation at the inflection point, that is the junction between the two bells, leading to the generation of a low content of aerodynamic side loads with respect to conventional bell nozzles. The nozzle wall-pressure signature is analyzed in the frequency domain and compared with the experimental data available in the literature for the same geometry and flow conditions. The Fourier spectra in time and space (azimuthal wavenumber) show the presence of a persistent tone associated to the symmetric shock movement. Asymmetric modes are only slightly excited by the shock and the turbulent structures. The low mean value of the side-loads magnitude is in good agreement with the experiments and confirms that the inflection point dampens the aero-acoustic interaction between the separation-shock and the detached shear layer.

Experimental Analysis on a Model of a Small Ducted Wind Turbine Equipped with Passive Flow Control Devices

2021 ◽  
Author(s):  
Elena-Alexandra Chiulan ◽  
Costin Ioan Cosoiu ◽  
Andrei-Mugur Georgescu ◽  
Anton Anton ◽  
Mircea Degeratu
Keyword(s):  
Flow Control ◽  
Wind Turbine ◽  
Experimental Analysis ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Flow Control Devices ◽  
Control Devices

scholarly journals Fundamental Studies of Vortices Induced by a Vortex-Generator for Automotive Applications

2014 ◽  
Vol 553 ◽  
pp. 211-216
Author(s):  
Asiful Islam ◽  
Graham Doig
Keyword(s):  
Turbulence Models ◽  
Vortex Generator ◽  
Automotive Applications ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Flow Control Devices ◽  
Simple Geometry ◽  
Image Velocimetry ◽  
Control Devices ◽  
Spatial Trajectory

For automotive applications, passive flow control devices can be used to reduce, delay or prevent flow separation. This study explores the nature of vortex generation and behaviour, numerically and experimentally, for a simple geometry at a Reynolds Number (Rex) of 5×105 and 1.945×106. The setup comprised a triangular vane vortex-generator mounted on a shallow ramp referenced from literature. Flow over the isolated ramp was validated with past experimental particle-image-velocimetry (PIV) data, which also highlighted the relative performance of various turbulence models. A parametric study was undertaken with the vane orientation defined by an angle-of-attack (β) and stream-wise location (xedge/xVG). These results revealed relationships between geometric parameters of the vortex generator, as well as the influence of the boundary layer thickness (hVG/δ), on the spatial trajectory of induced vortices.

Further Investigation of Vertical Stabilizer with Passive Flow Control Devices

2020 ◽  
Author(s):  
Yasushi Ito ◽  
Shunsuke Koike ◽  
Mitsuhiro Murayama ◽  
Yoshiyasu Ichikawa ◽  
Kazuyuki Nakakita ◽  
...  
Keyword(s):  
Flow Control ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Flow Control Devices ◽  
Control Devices

Influence of Passive Flow-Control Devices on the Pressure Fluctuations at Wing-Body Junction Flows

2007 ◽  
Vol 129 (8) ◽  
pp. 1030-1037 ◽  
Author(s):  
Semih M. Ölçmen ◽  
Roger L. Simpson
Keyword(s):  
Flow Control ◽  
High Surface ◽  
Pressure Fluctuations ◽  
Wall Pressure ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Wall Pressure Fluctuations ◽  
Flow Control Devices ◽  
Zero Degree ◽  
Control Devices

The effectiveness of passive flow-control devices in eliminating high surface rms pressure fluctuations at the junction of several idealized wing/body junction flows was studied. Wall-pressure fluctuation measurements were made using microphones along the line of symmetry at the wing/body junction of six different wing shapes. The wings were mounted on the wind tunnel floor at a zero degree angle-of-attack. The six wing shapes tested were: a 3:2 semi-elliptical-nosed NACA 0020 tailed generic body shape (Rood wing), a parallel center-body model, a tear-drop model, a Sandia 1850 model, and NACA 0015 and NACA 0012 airfoil shapes. Eight different fence configurations were tested with the Rood wing. The two double-fence configurations were found to be the most effective in reducing the pressure fluctuations. Two of the single fence types were nearly as effective and were simpler to manufacture and test. For this reason one of these single fence types was selected for testing with all of the other wing models. The best fence flow-control devices were found to reduce rms wall-pressure fluctuations by at least 61% relative to the baseline cases.

scholarly journals Study of Lubricant Jet Flow Phenomena in Spur Gears

1975 ◽  
Vol 97 (2) ◽  
pp. 283-288 ◽  
Author(s):  
L. S. Akin ◽  
J. J. Mross ◽  
D. P. Townsend
Keyword(s):  
Motion Picture ◽  
High Speed ◽  
Drop Size ◽  
Gear Tooth ◽  
Jet Flow ◽  
Spur Gear ◽  
Spur Gears ◽  
Gear Teeth ◽  
Flow Phenomena ◽  
Oil Jet

Lubricant jet flow impingement and penetration depth into a gear tooth space were measured at 4920 and 2560 using a 8.89-cm- (3.5-in.) pitch dia 8 pitch spur gear at oil pressures from 7 × 104 to 41 × 104 N/m2 (10 psi to 60 psi). A high speed motion picture camera was used with xenon and high speed stroboscopic lights to slow down and stop the motion of the oil jet so that the impingement depth could be determined. An analytical model was developed for the vectorial impingement depth and for the impingement depth with tooth space windage effects included. The windage effects on the oil jet were small for oil drop size greater than 0.0076 cm (0.003 in.). The analytical impingement depth compared favorably with experimental results above an oil jet pressure of 7 × 104 N/m2 (10 psi). Some of this oil jet penetrates further into the tooth space after impingement. Much of this post impingement oil is thrown out of the tooth space without further contacting the gear teeth.

scholarly journals Jet flow phenomena during nucleate boiling

2002 ◽  
Vol 45 (6) ◽  
pp. 1359-1363 ◽  
Author(s):  
H. Wang ◽  
X.F. Peng ◽  
B.X. Wang ◽  
D.J. Lee
Keyword(s):  
Jet Flow ◽  
Nucleate Boiling ◽  
Flow Phenomena
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