Three-dimensional shock tube flows for dense gases

2007 ◽  
Vol 583 ◽  
pp. 423-442 ◽  
Author(s):  
ALBERTO GUARDONE
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Shock Front ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Dense Gas ◽  
Complex Flow ◽  
The Many ◽  
The One ◽  
Rarefaction Shock

The formation process of a non-classical rarefaction shock wave in dense gas shock tubes is investigated by means of numerical simulations. To this purpose, a novel numerical scheme for the solution of the Euler equations under non-ideal thermodynamics is presented, and applied for the first time to the simulation of non-classical fully three-dimensional flows. Numerical simulations are carried out to study the complex flow field resulting from the partial burst of the shock tube diaphragm, a situation that has been observed in preliminary trials of a dense gas shock tube experiment. Beyond the many similarities with the corresponding classical flow, the non-classical wave field is characterized by the occurrence of anomalous compression isentropic waves and rarefaction shocks propagating past the leading rarefaction shock front. Negative mass flow through the rarefaction shock wave results in a limited interaction with the contact surface close to the diaphragm, a peculiarity of the non-classical regime. The geometrical asymmetry does not prevent the formation of a single rarefaction shock front, though the pressure difference across the rarefaction wave is predicted to be weaker than the one which would be obtained by the complete burst of the diaphragm.

Investigation on the Shock Control Using Grooved Surface in a Linear Turbine Nozzle

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Xinguo Lei ◽  
Mingxu Qi ◽  
Harold Sun ◽  
Liangjun Hu
Keyword(s):  
Shock Wave ◽  
Numerical Simulations ◽  
Smooth Surface ◽  
Engine Performance ◽  
Engine Emissions ◽  
Wave Characteristics ◽  
Grooved Surface ◽  
Rotor Stator Interaction ◽  
Nozzle Configuration ◽  
The One

Radial flow variable nozzle turbine (VNT) enables better matching between a turbocharger and engine and can improve the engine performance as well as decrease the engine emissions, especially when the engine works at low-end operation points. With increased nozzle loading, stronger shock wave and clearance leakage flow may be generated and consequently introduces strong rotor–stator interaction between turbine nozzle and rotor, which is a key concern of rotor high-cycle fatigue (HCF) failure. With the purpose of developing a low shock wave intensity turbine nozzle, the influence of grooved vane on the shock wave characteristics is investigated in the present paper. A Schlieren visualization experiment was first carried out on a linear turbine nozzle with smooth surface and the behavior of the shock wave was studied. Numerical simulations were also performed on the turbine nozzle. Guided by the visualization and numerical simulation, grooves were designed on the nozzle surface where the shock wave was originated and numerical simulations were performed to investigate the influence of grooves on the shock wave characteristics. Results indicate that for a smooth nozzle configuration, the intensity of the shock wave increases as the expansion ratios increase, while the onset position is shifted downstream to the nozzle trailing edge. For a nozzle configuration with grooved vane, the position of the shock wave onset is shifted upstream compared to the one with a smooth surface configuration, and the intensity of the shock wave and the static pressure (Ps) distortion at the nozzle vane exit plane are significantly depressed.

Investigation on the Shock Control Using Grooved Surface in a Linear Turbine Nozzle

2017 ◽  
Author(s):  
Xinguo Lei ◽  
Mingxu Qi ◽  
Harold Sun ◽  
Leon Hu
Keyword(s):  
Shock Wave ◽  
Numerical Simulations ◽  
Smooth Surface ◽  
Engine Performance ◽  
Engine Emissions ◽  
Wave Characteristics ◽  
Grooved Surface ◽  
Rotor Stator Interaction ◽  
Nozzle Configuration ◽  
The One

Radial flow Variable Nozzle Turbine (VNT) enables better matching between a turbocharger and engine, and can improve the engine performance as well as decrease the engine emissions, especially when the engine works at low-end operation points. With increased nozzle loading, stronger shock wave and clearance leakage flow may be generated. The shock wave consequently introduces strong rotor-stator interaction between turbine nozzle and impeller, which is also a key concern of impeller high cycle fatigue failure. With the purpose of developing a shock wave free or low shock wave intensity turbine nozzle, the influence of grooved vane on the shock wave characteristics is investigated in present paper. A Schlieren visualization experiment was first carried out on a linear turbine nozzle with smooth surface and the behavior of the shock wave was studied. Numerical simulations were also performed on the turbine nozzle. The predicted shock wave shape, position and intensity were compared against the Schlieren images. Guided by the visualization and numerical simulation, grooves were designed on the nozzle surface where the shock wave was originated and numerical simulations were performed to investigate the influence of grooves on the shock wave characteristics. Results indicate that for a smooth nozzle configuration, the intensity of the shock wave increases as the expansion ratios increase, while the onset position is shifted downstream to the nozzle trailing edge. For a nozzle configuration with grooved vane, the position of the shock wave onset is shifted upstream compared to the one with a smooth surface configuration, and the intensity of the shock wave as well as the static pressure distortion at the nozzle vane exit plane are significantly depressed.

Nanometer-Scale Shock-Front Structure in Metals

1988 ◽  
Vol 141 ◽  
Author(s):  
Paul A. Taylor ◽  
Brian W. Dodson
Keyword(s):  
Shock Wave ◽  
Molecular Dynamics ◽  
Shock Front ◽  
Nanometer Scale ◽  
Many Body ◽  
Front Structure ◽  
Atomic Interactions ◽  
The Many ◽  
First Time ◽  
Structural Instabilities

AbstractMolecular dynamics shock wave simulations have been performed, which for the first time include a realistic many-body description of the atomic interactions. The structural instabilities observed in the shock-front structure are dramatically influenced by the many-body effects of these atomic interactions.

Shock tube flows past partially opened diaphragms

2008 ◽  
Vol 602 ◽  
pp. 267-286 ◽  
Author(s):  
PAOLO GAETANI ◽  
ALBERTO GUARDONE ◽  
GIACOMO PERSICO
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Shock Front ◽  
Compressible Flows ◽  
Wave Speed ◽  
Initial Pressure ◽  
Normal Shock ◽  
Relative Area ◽  
Simple Analytical Model ◽  
Pressure Oscillations

Unsteady compressible flows resulting from the incomplete burst of the shock tube diaphragm are investigated both experimentally and numerically for different initial pressure ratios and opening diameters. The intensity of the shock wave is found to be lower than that corresponding to a complete opening. A heuristic relation is proposed to compute the shock strength as a function of the relative area of the open portion of the diaphragm. Strong pressure oscillations past the shock front are also observed. These multi-dimensional disturbances are generated when the initially normal shock wave diffracts from the diaphragm edges and reflects on the shock tube walls, resulting in a complex unsteady flow field behind the leading shock wave. The limiting local frequency of the pressure oscillations is found to be very close to the ratio of acoustic wave speed in the perturbed region to the shock tube diameter. The power associated with these pressure oscillations decreases with increasing distance from the diaphragm since the diffracted and reflected shocks partially coalesce into a single normal shock front. A simple analytical model is devised to explain the reduction of the local frequency of the disturbances as the distance from the leading shock increases.

Rarefaction shock wave near the critical liquid–vapour point

1983 ◽  
Vol 126 ◽  
pp. 59-73 ◽  
Author(s):  
A. A. Borisov ◽  
Al. A. Borisov ◽  
S. S. Kutateladze ◽  
V. E. Nakoryakov
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Critical Point ◽  
Wave Front ◽  
Propagation Velocity ◽  
Test Substance ◽  
Unperturbed State ◽  
Long Wave ◽  
Rarefaction Shock ◽  
Negative Shock

The existence of a rarefaction shock wave or negative shock wave in a substance whose unperturbed state is close to the thermodynamic critical liquid–vapour point has been demonstrated experimentally. Its evolution and propagation velocity in a shock tube with Freon-13 as the test substance are described. It is shown that the steepness of the wave front does not diminish as the wave evolves. An equation is derived that describes the evolution of long-wave perturbations near the critical point.

Experimental and Numerical Investigation of a Shock Wave Within a Swept Shrouded Propfan Rotor

1996 ◽  
Vol 118 (1) ◽  
pp. 66-72
Author(s):  
K. Helming
Keyword(s):  
Shock Wave ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Flow Region ◽  
Navier Stokes ◽  
Velocity Measurements ◽  
Suction Surface ◽  
Measured Flow ◽  
Laser Velocity ◽  
The One

Laser velocity measurements are conducted in a swept propfan rotor in order to investigate the local transonic flow region on the suction surface at high subsonic inlet Mach numbers. The velocity measurements are accompanied by a three-dimensional Navier–Stokes calculation for a selected operating point. The good agreement between computed and measured flow field gives some confidence to study the local three-dimensional passage shock on the suction surface by using the numerical procedure. Apart from the computed three-dimensional shock, structure is investigated in detail. By considering streamlines, it is concluded whether the shock wave is normal or oblique. The results are compared with the one-dimensional shock conditions.

The Nature of the Early Royal Society: Part I

1976 ◽  
Vol 9 (1) ◽  
pp. 1-24 ◽  
Author(s):  
K. Theodore Hoppen
Keyword(s):  
Seventeenth Century ◽  
Royal Society ◽  
Natural Philosophy ◽  
Three Dimensional ◽  
Scientific Enterprise ◽  
Scientific Debate ◽  
The Many ◽  
The One ◽  
Natural Philosophers ◽  
Working Out

The foundation of the Royal Society marks an important step in the institutionalization of seventeenth-century British natural philosophy. The society's existence and activities provided a focus for the exchange of opinions, while its meetings and publications became forums for scientific debate. Some writers, however, have claimed much more than this for the society and have seen its establishment as marking a real watershed between, on the one hand, intellectually ‘conservative elements’ and, on the other, a set of ‘definite philosophical principles … inspiring … progressive minds’. Others have gone still further and argued not only that the society's activities ‘enormously’ accelerated ‘the development of natural sciences’, but that these activities were the result of the ‘working out of a conscious, deliberately-conceived ideal’. But views which see a single, logically consistent conception of the nature of the scientific enterprise informing the work and outlook of the Royal Society and its members involve a serious oversimplification of the complexity of natural philosophy in the late seventeenth century. Despite some important work published in recent years, we are still far from achieving a satisfactory understanding of the complicated web of traditions, sources, and intellectual systems that provided both an inspirational dynamic for the work of natural philosophers such as those in the Royal Society and patterns of expression through which their preoccupations could be articulated. Thus the many studies which have been devoted to establishing connexions between the scientific movement and patterns of religious or political belief have been flawed from the start by unreal assumptions about the degree of intellectual coherence presented by the natural philosophy of the time. And until we can present a more three-dimensional picture of what the 'scientific movement’ was in fact all about, and until wider agreement has been reached as to satisfactory definitions of various types of socio-theological attitude and behaviour, such studies are no more than attempts to tie together two unknowns by means of a rope of sand.

Direct numerical simulation of isotropic turbulence interacting with a weak shock wave

1993 ◽  
Vol 251 ◽  
pp. 533-562 ◽  
Author(s):  
Sangsan Lee ◽  
Sanjiva K. Lele ◽  
Parviz Moin
Keyword(s):  
Shock Wave ◽  
Kinetic Energy ◽  
Shock Waves ◽  
Shock Front ◽  
Numerical Simulations ◽  
Turbulent Kinetic Energy ◽  
Isotropic Turbulence ◽  
Weak Shock ◽  
Linear Analysis ◽  
Weak Shock Wave

Interaction of isotropic quasi-incompressible turbulence with a weak shock wave was studied by direct numerical simulations. The effects of the fluctuation Mach number Mt of the upstream turbulence and the shock strength M21 — 1 on the turbulence statistics were investigated. The ranges investigated were 0.0567 ≤ Mt ≤ 0.110 and 1.05 ≤ M1 ≤ 1.20. A linear analysis of the interaction of isotropic turbulence with a normal shock wave was adopted for comparisons with the simulations.Both numerical simulations and the linear analysis of the interaction show that turbulence is enhanced during the interaction with a shock wave. Turbulent kinetic energy and transverse vorticity components are amplified, and turbulent lengthscales are decreased. The predictions of the linear analysis compare favourably with simulation results for flows with M2t < a(M21 — 1) with a ≈ 0.1, which suggests that the amplification mechanism is primarily linear. Simulations also showed a rapid evolution of turbulent kinetic energy just downstream of the shock, a behaviour not reproduced by the linear analysis. Investigation of the budget of the turbulent kinetic energy transport equation shows that this behaviour can be attributed to the pressure transport term.Shock waves were found to be distorted by the upstream turbulence, but still had a well-defined shock front for M2t < a(M21— 1) with a ≈ 0.1). In this regime, the statistics of shock front distortions compare favourably with the linear analysis predictions. For flows with M2t > a(M21— 1 with a ≈ 0.1, shock waves no longer had well-defined fronts: shock wave thickness and strength varied widely along the transverse directions. Multiple compression peaks were found along the mean streamlines at locations where the local shock thickness had increased significantly.

scholarly journals Experimental and Numerical Investigation of Shock Wave Within a Swept Shrouded Propfan Rotor

1994 ◽  
Author(s):  
Klaus Helming
Keyword(s):  
Shock Wave ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Flow Region ◽  
Navier Stokes ◽  
Velocity Measurements ◽  
Suction Surface ◽  
Measured Flow ◽  
Laser Velocity ◽  
The One

Laser velocity measurements are conducted in a swept propfan rotor in order to investigate the local transonic flow region on the suction surface at high subsonic inlet Mach numbers. The velocity measurements are accompanied by a 3D-Navier-Stokes calculation for a selected operating point. The good agreement between computed and measured flow field gives some confidence to study the local three-dimensional passage shock on the suction surface by using the numerical procedure. Apart of the computed three-dimensional shock structure is investigated in detail. By considering streamlines it is concluded whether the shock wave is normal or oblique. The results are compared with the one-dimensional shock conditions.

scholarly journals Volumetric 3-component velocimetry measurements of the flow field on the rear window of a generic car model

2012 ◽  
Vol 16 (1) ◽  
pp. 313-320 ◽  
Author(s):  
Nabil Tounsi ◽  
Grégoire Fourrié ◽  
Hamid Oualli ◽  
Laurent Keirsbulck ◽  
Samir Hanchi ◽  
...  
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Separated Flow ◽  
Control Device ◽  
Wake Flow ◽  
Complex Flow ◽  
Rear Window ◽  
Longitudinal Vortices ◽  
Car Model ◽  
The One

Volumetric 3-component Velocimetry measurements are carried out in the flow field around the rear window of a generic car model, the so-called Ahmed body. This particular flow field is known to be highly unsteady, three dimensional and characterized by strong vortices. The volumetric velocity measurements from the present experiments provide the most comprehensive data for this flow field to date. The present study focuses on the wake flow modifications which result from using a simple flow control device, such as the one recently employed by Fourri? et al. [1]. The mean data clearly show the structure of this complex flow and confirm the drag reduction mechanism suggested by Fourri? et al. The results show that strengthening the separated flow leads to weakening the longitudinal vortices and vice versa. The present paper shows that the Volumetric 3-component Velocimetry technique is a powerful tool used for a better understanding of a threedimensional unsteady complex flow such that developing around a bluffbody.

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