共查询到20条相似文献,搜索用时 15 毫秒
1.
The research on gaseous detonation has recently become a very important issue, mainly due to safety reasons in connection
with increasing use of gaseous fuels. To simulate detonation, the direct Monte-Carlo simulation technique has been proposed,
together with simple model of molecular collisions, making it possible to heat the gas in a way similar to the processes in
the flame. Such model is capable of producing waves, having the features characteristic for detonation (Dremin in Towards
detonation theory. Springer, 1999). In the present work the influence of finite reaction time and the inverse reaction upon
formation and extinguishing detonation, in the framework of this model, has been investigated. 相似文献
2.
Zekai Hong Genny A. Pang Subith S. Vasu David F. Davidson Ronald K. Hanson 《Shock Waves》2009,19(2):113-123
Non-ideal shock tube facility effects, such as incident shock wave attenuation, can cause variations in the pressure histories
seen in reflected shock wave experiments. These variations can be reduced, and in some cases eliminated, by the use of driver
inserts. Driver inserts, when designed properly, act as sources of expansion waves which can counteract or compensate for
gradual increases in reflected shock pressure profiles. An algorithm for the design of these inserts is provided, and example
pressure measurements are presented that demonstrate the success of this approach. When these driver inserts are employed,
near- ideal, constant-volume performance in reflected shock wave experiments can be achieved, even at long test times. This
near-ideal behavior simplifies the interpretation of shock tube chemical kinetics experiments, particularly in experiments
which are highly sensitive to temperature and pressure changes, such as measurements of ignition delay time of exothermic
reactions. 相似文献
3.
This paper is devoted to present some results on the controllability of the hydrostatic Stokes equations. The first main result
of this paper states that the approximate null controllability of this system holds. This is proved whatever the boundary
conditions are. Then, we extend this result to an exact null controllability result when the boundary conditions are ∂
z
u = 0 (the vertical derivative of the horizontal velocity) at the bottom.
相似文献
4.
In the present work, using the molecular-dynamics approach, we examine the initiation and development of detonation, initiated by a pulse of an external force, in a 3-D solid-state explosive. It is found that, prior to the onset of the chemical reaction, the substance passes from crystalline into the liquid state. Based on a mesoscale analysis, we analyze the applicability of main conservation equations, written in their integral, most general form or in the stationary form for the entire computation domain, including the undisturbed region of the crystal, reacting zone, and detonation products, to detonating solid explosives.Received: 30 August 2002, Accepted: 3 July 2003, Published online: 5 August 2003 相似文献
5.
The head-on collision of a combustion front with a closely packed bed of ceramic-oxide spheres was investigated in a vertical
76.2 mm diameter tube containing a nitrogen diluted stoichiometric ethylene–oxygen mixture. A layer of spherical beads in
the diameter range of 3–12.7 mm was placed at the bottom of the tube and a flame was ignited at the top endplate. Four orifice
plates spaced at one tube diameter were placed at the ignition end of the tube in order to accelerate the flame to either
a “fast-flame” or a detonation wave before the bead layer face. The mixture reactivity was adjusted by varying the initial
mixture pressure between 10 and 100 kPa absolute. The pressure before and within the bead layer was measured by flush wall-mounted
pressure transducers. For initial pressures where a fast-flame interacts with the bead layer peak pressures recorded at the
bead layer face were as high as five times the reflected Chapman–Jouget detonation pressure. The explosion resulting from
the interaction developed by two distinct mechanisms; one due to the shock reflection off the bead layer face, and the other
due to shock transmission and mixing of burned and unburned gas inside the bead layer. The measured explosion delay time (time
after shock reflection from the bead layer face) was found to be independent of the incident shock velocity. As a result,
the explosion initiation is not the direct result of the shock reflection process but instead is more likely due to the interaction
of the reflected shock wave and the trailing flame. The bead layer was found to be very effective in attenuating the explosion
front transmitted through the bead layer and thus isolating the tube endplate.
This paper is based on work that was presented at the 21th International Colloquium on the Dynamics of Explosions and Reactive
Systems, Poitiers, France, July 23–27, 2007. 相似文献
6.
Didier Bresch El Hassan Essoufi Mamadou Sy 《Journal of Mathematical Fluid Mechanics》2007,9(3):377-397
In this paper, we look at the influence of the choice of the Reynolds tensor on the derivation of some multiphasic incompressible
fluid models, called Kazhikhov–Smagulov type models. We show that a compatibility condition between the viscous tensor and
the diffusive term allows us to obtain similar models without assuming a small diffusive term as it was done for instance
by A. Kazhikhov and Sh. Smagulov. We begin with two examples: The first one concerning pollution and the last one concerning
a model of combustion at low Mach number. We give the compatibility condition that provides a class of models of the Kazhikhov–Smagulov
type. We prove that these models are globally well posed without assumptions between the density and the diffusion terms. 相似文献
7.
Francesca Crispo 《Journal of Mathematical Fluid Mechanics》2008,10(3):311-325
We consider the motion of a non-Newtonian fluid with shear dependent viscosity between two cylinders. We prove regularity
results for the second derivatives of the velocity and the first derivatives of the pressure up to the boundary. A similar
problem is studied in reference [2] in the case of a flat boundary. Here we extend the techniques applied in [2] to cylindrical
coordinates.
相似文献
8.
The problem of forced nonaxisymmetric vibrations of reinforced ellipsoidal shells under nonstationary loads is formulated.
A numerical algorithm of solving it is developed and the results obtained are analyzed
Translated from Prikladnaya Mekhanika, Vol. 44, No. 10, pp. 63–73, October 2008. 相似文献
9.
We estimate L
p
spatial-temporal decay rates of solutions of the linearized equations of incompressible flow in a 2D exterior domain. When
a domain has a boundary, pressure term makes an obstacle since we do not have enough information on the pressure term near
the boundary. To overcome the difficulty, we use a special form of a test function.
The first author was supported by Korea Research Foundation Grant (KRF-2003-015-C00052), and the second author by KRF-2006-531-C0009. 相似文献
10.
Measurement of the gradient field of a turbulent free surface 总被引:1,自引:1,他引:0
We study the free surface above a turbulent channel flow. We describe a laser scanning technique that can be used to measure the space–time turbulent surface gradient field along a line. A harmonically swiveling laser beam is focused on the surface and its angle of refraction is measured using a position sensing device. The registered signals can be converted easily to the desired gradient field, and spectra and correlations can be measured. Examples of measured spectra and correlation functions of the surface above a turbulent channel flow (Reynolds number R
λ ≈ 250) demonstrate the viability of the technique. We further assess the validity of Taylor’s frozen turbulence hypothesis that implies that time-dependent signals measured along a line that is oriented perpendicularly to the mean channel velocity can be interpreted as 2D measurements of the surface slope. While Taylor’s hypothesis works for a turbulent velocity field, it does not work for its free surface.
相似文献
Willem van de WaterEmail: |
11.
T. Roubíček 《Journal of Mathematical Fluid Mechanics》2009,11(1):110-125
The model combining incompressible Navier–Stokes’ equation in a non-Newtonian p-power-law modification and the nonlinear heat equation is considered. Existence of its (very) weak solutions is proved for
p > 11/5 under mild assumptions of the temperature-dependent stress tensor by careful successive limit passage in a Galerkin
approximation.
相似文献
12.
Hyeong-Ohk Bae 《Journal of Mathematical Fluid Mechanics》2008,10(4):503-530
We estimate the time decay rates in L
1, in the Hardy space and in L
∞ of the gradient of solutions for the Stokes equations on the half spaces. For the estimates in the Hardy space we adopt the
ideas in [7], and also use the heat kernel and the solution formula for the Stokes equations.
We also estimate the temporal-spatial asymptotic estimates in L
q
, 1 < q < ∞, for the Stokes solutions.
This work was supported by grant No. (R05-2002-000-00002-0(2002)) from the Basic Research Program of the Korea Science & Engineering
Foundation. 相似文献
13.
We consider asymptotic behavior of Leray’s solution which expresses axis-symmetric incompressible Navier–Stokes flow past
an axis-symmetric body. When the velocity at infinity is prescribed to be nonzero constant, Leray’s solution is known to have
optimum decay rate, which is in the class of physically reasonable solution. When the velocity at infinity is prescribed to
be zero, the decay rate at infinity has been shown under certain restrictions such as smallness on the data. Here we find
an explicit decay rate when the flow is axis-symmetric by decoupling the axial velocity and the horizontal velocities.
The first author was supported by KRF-2006-312-C00466. The second author was supported by KRF-2006-531-C00009. 相似文献
14.
We consider the asymptotic limit for the complete Navier–Stokes–Fourier system as both Mach and Froude numbers tend to zero.
The limit is investigated in the context of weak variational solutions on an arbitrary large time interval and for the ill-prepared
initial data. The convergence to the Oberbeck–Boussinesq system is shown.
相似文献
15.
A combined computational and experimental study was performed to investigate the effect of a single laser energy pulse on the transition from a Mach Reflection (MR) to a Regular Reflection (RR) in the Dual Solution Domain (DSD). The freestream Mach number is 3.45 and two oblique shock waves are formed by two symmetric
wedges. These conditions correspond to a point midway within the DSD wherein either an MR or an RR is possible. A steady MR was first obtained experimentally and numerically, then a single laser pulse was deposited above the horizontal center plane. In the experiment, the laser beam was focused resulting in a deposition volume of approximately 3 mm3, while in the simulation, the laser pulse was modeled as an initial variation of the temperature and pressure using Gaussian profile. A grid refinement study was conducted to assess the accuracy of the numerical simulations. For the steady MR, the simulation showed the variation of Mach stem height along the span due to side effects. The predicted spanwise averaged Mach stem height was 1.96 mm within 2% of the experimental value of 2 mm. The experiment showed that the Mach stem height decreased to 30% of its original height due to the interaction with the thermal spot generated by the laser pulse and then returned to its original height by
s. That the Mach stem returned to its original height was most likely due to freestream turbulence in the wind tunnel. The numerical simulation successfully predicted the reverse transition from a stable MR to a stable RR and the stable RR persisted across the span. This study showed the capability of a laser energy pulse to control the reverse transition of MR
RR within the Dual Solution Domain. 相似文献
16.
Let be an infinite cylinder of , n ≥ 3, with a bounded cross-section of C
1,1-class. We study resolvent estimates and maximal regularity of the Stokes operator in for 1 < q, r < ∞ and for arbitrary Muckenhoupt weights ω ∈ A
r
with respect to x′ ∈ Σ. The proofs use an operator-valued Fourier multiplier theorem and techniques of unconditional Schauder decompositions
based on the -boundedness of the family of solution operators for a system in Σ parametrized by the phase variable of the one-dimensional
partial Fourier transform.
Supported by the Gottlieb Daimler- und Karl Benz-Stiftung, grant no. S025/02-10/03. 相似文献
17.
Xinyu He 《Journal of Mathematical Fluid Mechanics》2007,9(3):398-410
Let
be the exterior of the closed unit ball. Consider the self-similar Euler system
Setting α = β = 1/2 gives the limiting case of Leray’s self-similar Navier–Stokes equations. Assuming smoothness and smallness of the boundary
data on ∂Ω, we prove that this system has a unique solution
, vanishing at infinity, precisely
The self-similarity transformation is v(x, t) = u(y)/(t* − t)α, y = x/(t* − t)β, where v(x, t) is a solution to the Euler equations. The existence of smooth function u(y) implies that the solution v(x, t) blows up at (x*, t*), x* = 0, t* < + ∞. This isolated singularity has bounded energy with unbounded L
2 − norm of curl v. 相似文献
18.
Adrian Constantin Rossen I. Ivanov Emil M. Prodanov 《Journal of Mathematical Fluid Mechanics》2008,10(2):224-237
We show that the governing equations for two-dimensional gravity water waves with constant non-zero vorticity have a nearly-Hamiltonian
structure, which becomes Hamiltonian for steady waves.
相似文献
19.
In this article we investigate numerically a Hopf bifurcation phenomenon for a viscous incompressible flow down an inclined
plane. This problem has been discussed by Nishida et al. who proved the existence of periodic solutions bifurcating from the
steady flow. Using a computational methodology based on finite elements for the space discretization and on operator splitting
for the time discretization, we have been able to reproduce the results predicted by Nishida et al.
相似文献
20.
Michael Renardy 《Journal of Mathematical Fluid Mechanics》2009,11(1):91-99
We prove the global existence in time of solutions to time-dependent shear flows for certain viscoelastic fluids. The essential
point in the proof is an a priori estimate for the shear stress. Positive definiteness constraints for the stress play a crucial
role in obtaining such estimates.
This research was supported by the National Science Foundation under Grant DMS-0405810. 相似文献