Three-Dimensional Structure of Non-Equilibrium Homogeneous Condensation Flow in a Supersonic Rectangular Nozzle

Numerical simulations have been carried out for a supersonic three-dimensional rectangular arc nozzle, where a secondary flow toward the center of the curvature occurs due to the shape of the nozzle. It is known that secondary flow causes longitudinal vortices to form near the wall of the nozzle corner, making the nozzle outlet flow unstable and induces loss of transport energy. When the working fluid is a condensable gas with relatively large latent heat such as moist air or steam, rapid accelerated expansion in the nozzle causes non-equilibrium condensation due to supersaturation. After the release of latent heat during phase transition, nozzle flow continues expanding at an equilibrium saturation condition. In the absence of foreign particles, e.g. ions or dust particles, condensation nuclei are formed in the gas itself causing non-equilibrium homogeneous condensation. Supersonic nozzle flow properties vary considerably due to the occurrence of condensation phenomenon. The objective of this study is to investigate the effect of non-equilibrium homogeneous condensation on the longitudinal vortices which form in the range close to the corner of rectangular arc nozzle numerically.

Effects of Heterogeneous Condensation on the Transonic Flow Fields on a Bump Model

In the present study, effect of the heterogeneous condensation on the characteristics of shock wave generated on the bump model in the transonic flow field was investigated numerically. As a result, it was found that, for the flow field with steady adiabatic shock wave on the bump model, the condensation with heterogeneous nucleation has a strong effect on the whole flow field, and it reduced the strength of the shock. Furthermore, the total pressure loss was dependent on the concentration of the solid particles per unit volume.

Study on the Wiping Gas Jet in Continuous Galvanizing Line

In the continuous hot-dip galvanizing process, the gas-jet wiping is used to control the coating thickness of moving steel strip. The high speed gas-jet discharged from the nozzle slot impinges on the strip, and at this moment, wipes the liquid coating layer dragged by a moving strip. The coating thickness is generally influenced on the flow characteristics of wiping gas-jet such as the impinging pressure distribution, pressure gradient and shear stress distribution on the surface of strip. The flow characteristics of wiping gas-jet mentioned above depends upon considerably both the process operating conditions such as the nozzle pressure, nozzle-to-strip distance and line speed, and the geometry of gas-jet wiping apparatus such as the height of nozzle slot. In the present study, the effect of the geometry of nozzle on the coating thickness is investigated with the help of a computational fluid dynamics method. The height of nozzle slot is varied in the range of 0.6mm to 1.7mm. A finite volume method (FVM) is employed to solve two-dimensional, steady, compressible Navier-Stokes equations. Based upon the results obtained, the effect of the height of nozzle slot in the gas-jet wiping process is discussed in detail. The computational results show that for a given standoff distance between the nozzle to the strip, the effective height of nozzle slot exists in achieving thinner coating thickness.

Effect of Axisymmetric Sonic Nozzle Geometry on Characteristics of Supersonic Air Jet

The effect of nozzle geometry on sonic line and characteristics of supersonic air jet was studied. Computational fluid dynamics was applied in this study. The axisymmetric nozzle geometries investigated were two different contour converging nozzles, two different conically converging sharp-edged nozzles and a sharp-edged orifice. The results show that the supersonic jet structure, sonic line and streamlines in supersonic jet are strongly influenced by the nozzle geometry, and the total pressure loss increases with the increase of Mach disk diameter. The present numerical simulation is an effective tool to evaluate compressible flows in supersonic air jet.

Study of Spiral Flow Generated through an Annular Slit

The effect of pressurized air inlets in the reservoir upstream of the annular slit on characteristics of the axial and tangential velocity components is investigated numerically, and the mechanism of occurrence of spiral nozzle flow is clarified. In simulations, Unified Platform for Aerospace Computational Simulation (UPACS) is used. The governing equations under consideration are the unsteady compressible Navier - Stokes. A second-order finite volume scheme with MUSCL (Roe scheme) is used to discretize the spatial derivatives, and a second order-central difference scheme for the viscous terms, and a MFGS (Matrix Free Gauss Seidel) is employed for time integration. Spalart-Allmaras model was used as a turbulence model. The results obtained are compared with velocity distributions in the experiment measured by the two-component fiber optic laser Doppler velocimeter system. The existence of discrete pressurized air inlets that leads to the occurrence of asymmetrical characteristics is a very important factor for the formation of spiral flow.

Effect of Annular Slit Geometry on Characteristics of Spiral Jet

A spiral flow using an annular slit connected to a conical cylinder does not need special device to generate a tangential velocity component of the flow and differs from swirling flows. Pressurized fluid is supplied to an annular chamber and injected into the convergent nozzle through the annular slit. The annular jet develops into the spiral flow. In the present study, a spiral jet discharged out of nozzle exit was obtained by using a convergent nozzle and an annular slit set in nozzle inlet, and the effect of annular slit geometry on characteristics of the spiral jet was investigated by using a Laser Doppler Velocimeter (LDV) experimentally. Furthermore, velocity distributions of the spiral jet were compared with those of a normal jet.

Passive Control of Condensation Shock Wave in Prandtl-Meyer Expansion Flow

In this paper,the effects of the passive technique by using the slotted wall on the characteristics of a condensation shock wave generated in a Prandtl-Meyer flow were investigated experimentally.Furthermore,in order to clarify the variation of condensation properties in the flow field.navier-Stoker equations were solved numerically using a 3rd-order MUSCL type TVD finite-difference scheme with a second-order fractional-step for time integration.Baldwin-Lomax odel was used as a turbulence model in the computations.From experimental results,it was found that the shock strength on the slotted wall became weak in compariosn with no passive case(solid wall),and the present passive technique was the most effective when a foot of the condensation shock wave was located at the middle of slotted wall.Furthermore.it was confirmed numerically that the passive technique was also effective for the unsteady condensation shock wave.

A Study of the Impulse Wave Discharged from the Exits of Two Parallel Tubes

The twin impulse wave leads to very complicated flow fields, such as Mach stem, spherical waves, and vortex ring. The twin impulse wave discharged from the exits of the two tubes placed in parallel is investigated to understand the detailed flow physics associated with the twin impulse wave, compared with those in a single impulse wave. In the current study, the merging phenomena and propagation characteristics of the impulse waves are investigated using a shock tube experiment and by numerical computations. The Harten-Yee''s total variation diminishing (TVD) scheme is used to solve the unsteady two-dimensional compressible Euler equations. The Mach number Ms of incident shock wave is changed below 1.5 and the distance between two-parallel tubes, L/d, is changed from 1.2 to 4.0. In the shock tube experiment, the twin impulse waves are visualized by a Schlieren optical system for the purpose of validation of computational work. The results obtained show that on the symmetric axis between two-parallel tubes, the peak pressure produced by the twin impulse waves and its location strongly depend upon the distance between two-parallel tubes, L/d and the incident shock Mach number, Ms. The predicted Schlieren images represent the measured twin-impulse wave with a good accuracy.

A Study of the Vortical Flow over a Delta Wing with a Leading Edge Extension

The present paper describes computational and experimental work on the vortex flow characteristics of a sharp-edged delta wing with a leading edge extension (LEX). Experiment was carded out using a low-speed wind tunnel that has a test section of 3.5 m(W) × 2.45 m(H) × 8.7 m(L). The angle of attack of the delta wing ranges from 10° to 30°. The free stream velocity is fixed at 20 m/s, which corresponds to Reynolds number of 0.88 × 10^6 Computations using the mass-averaged implicit 3D Navier-Stokes equations were applied to predict the complicated vortical flow over the delta wing. The governing equations were discretized in space using a fully implicit finite volume differencing formation. The standard k-ε turbulent model was employed to close the governing equations. The present computations predicted the experimented flow field with a good accuracy.

Experimental Investigation on Noise Suppression in Supersonic Jets from Convergent-Divergent Nozzles with Baffles

The acoustic properties of supersonic jet noise from a convergent-divergent nozzle with a baffle have been studied experimentally over the range of nozzle pressure ratios from 2.0 to 8.0. Acoustic measurements were conducted in a carefully designed anechoic room providing a free-field environment. A new approach for screech noise suppression by a cross-wire is proposed. Schlieren photographs were taken to visualize the shock wave patterns in the supersonic jet with and without the cross-wire. The effects of the baffle and the cross-wire on acoustic properties are discussed. It is shown that the baffle has little effect on the screech frequency for the underexpanded supersonic jet without the cross-wire. Also, the cross-wire introduced in supersonic jets is found to lead to a significant reduction in overall sound pressure level.

A Study of the Gas Flow through Air Jet Loom

作为无梭的织布机之一，空气喷气织布机用一口空气喷气的粘性和动能搬运一支纱进经纱。这个拣的系统的性能取决于即时 inhalation/exhaust 的能力，嘴的配置，一个检查阀门的操作特征，等等。在最近的过去，许多研究在从一个嘴出口解除的空气喷气上被报导了，但是为理解流动的研究回答与联系的特征砍在嘴的层和冲击波层相互作用没足够被进行。在这份报纸，计算研究被执行与一个加速试管在空气喷气嘴解释流动领域并且与可得到的以前的试验性的数据验证了。从计算学习获得的结果证明在超声的流动政体，流动领域显著地取决于加速试管的长度。作为嘴压力比率增加，拖也对绳起作用的力量增加。为一个更长的加速试管，全部的压力损失大，由于摩擦损失。

A Study of Under-expanded Moist Air Jet Impinging on a Flat Plate

当气体通过在的一张会聚的嘴膨胀时比率对停滞压力周围比批评的，从嘴的发出的喷气是下面膨胀的的高。如果一个扁平的盘子是到在从嘴的某个距离的喷气的放的正常，一个分开的冲击波在在嘴出口和板之间的一个区域被形成。一般来说，有非平衡冷凝作用的超声的潮湿的空气喷气技术很经常被用于工业生产过程。尽管有在侵犯到稳固的身体的超声的潮湿的空气喷气的主要特征的重要性，它的质的特征不令人满意地被知道。在现在的学习，在一个垂直扁平的盘子上侵犯的下面膨胀的空气喷气上的非平衡冷凝作用的效果与非平衡冷凝作用在情况中数字地被调查，没有非平衡冷凝作用，为流动领域的摆动的频率变得比那大，并且静态的压力的振幅干燥空气与那些相比变得小。而且，数字结果与试验性的相比。关键词可压缩的流动 - 非平衡冷凝作用 - 侵犯喷气 - 模拟 CLC 数字

Study for the Gas Flow through a Critical Nozzle

In the present study, computational work using the axisymmetric, compressible, Navier-Stokes equations is carded out to predict the discharge coefficient and critical pressure ratio of gas flow through a critical nozzle. The Reynolds number effects are investigated with several nozzles with different throat diameter. Diffuser angle is varied to investigate the effects on the discharge coefficient and critical pressure ratio. The computational results are compared with the previous experimental ones. It is known that the discharge coefficient and critical pressure ratio are given by functions of the Reynolds number and boundary layer integral properties. It is also found that diffuser angle affects the critical pressure ratio.

A Computational Investigation on the Control of Cavity-Induced Pressure Oscillations Using Sub-Cavity

计算调查被进行了决定 attenuating 的一种被动控制技术的有效性在限制二维的超声的流动的导致洞的压力摆动。被动控制技术被试穿二扁平的盘子在在洞入口的马赫数字 1.83 点在一个方形的洞的前面墙附近完成。结果证明扁平的盘子在洞的前面墙附近属于，阻止了广泛地被相信是洞回声的原因的反馈循环的形成。压力摆动的变细的结果的数量也依赖于用作摆动 suppressor 的扁平的板的长度。