The critical separation reynolds number for streaming flow past a circular cylinder

Employing a complex variable approach to the equations of motion for an incompressible viscous fluid and a more general approximation to the convecting stream function it is possible to calculate an approximation to the vorticity on the boundary for streaming flow past a circular cylinder without solving first for the complete flow field. In particular it is found that separation at the rear stagnation point first occurs when $\text{R1 = 2.78}$, where $\text{R1}$ is the critical Reynolds number. This result is in good agreement with the value of $\text{R1}$ obtained by experiment and the value obtained numerically. The convecting stream function satisfies the conditions of no slip and vorticity is not convected through the cylinder as it is in small Reynolds number Oseen theory.     

Transonic flow past a convex corner with free streamline

An asymptotic analysis in the limit of large Reynolds numbers Re → ∞ is made of the system of Navier—Stokes equations in the neighborhood of a corner in a profile past which there is a transonic gas flow. The flow with free streamline from the corner point at which the velocity of sound is reached is taken as a limiting case. In the first approximation, it is described by a self-similar solution to the Kármán—Fal'kovich equation with self-similarity exponent n = 6/5 [1]. In such a flow, the favorable pressure gradient becomes infinite as the corner is approached from the side of the oncoming flow.     

Transonic flow past an airfoil with mini-flaps

The effect of mini-flaps located on either the lower or upper side of an airfoil near its trailing edge on the flow around the trailing edge and the global flow past the airfoil is numerically investigated. The flow pattern near the trailing edge is compared with that on which the Chaplygin-Joukowski hypothesis is based. The mini-flap effect on the aerodynamic characteristics of the airfoil is studied.     

Hypersonic similitude in the case of flow past a combination of a circular cone and a delta-shaped wing

The validity of the well-known law of hypersonic similitude [1, 2] for a combination of a circular cone and a delta-shaped wing has hitherto been verified only for the integral characteristics [3]. The law is verified in this paper for both the integral and local parameters of the flow. The posed problem has been solved numerically using the stationary analog of Godunov's method [4]. The shock waves and characteristic surfaces bounding the region of the properly conical flow were separated. As in the paper of Ivanov and Kraiko [5], the required distributions of the parameters were found by stabilization with respect to the coordinate.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 188–190, March–April, 1984.I thank A. N. Kraiko for his interest in the work and for discussing the results.     

Capillary cavity flow past a circular cylinder

Cavity flow past a circular cylinder is considered accounting for the surface tension on the cavity boundary. The fluid is assumed to be inviscid and incompressible, and the flow is assumed to be irrotational. The solution is based on two derived governing expressions, which are the complex velocity and the derivative of the complex potential defined in an auxiliary parameter region. An integral equation in the velocity magnitude along the free surface is derived from the dynamic boundary condition. The Brillouin–Villat criterion is employed to determine the location of the point of flow separation. The cases of zero surface tension and zero cavitation number are obtained as limiting cases of the solution. Numerical results concerning the effects of surface tension and cavitation development on the cavity detachment, the drag force and the geometry of the free boundaries are presented over a wide range of the Weber and the cavitation numbers.     

Supersonic flow past a slender cone with asymmetric nosetip

Supersonic flow of an inviscid gas that does not conduct heat past a slender cone with asymmetric nosetip has been investigated at zero and nonzero angle of attack. The flow is calculated by the Babenko-Voskresenskii numerical method. It is shown that the asymmetry of the nosetip has a strong influence on the distribution of the parameters of the gas over the surface of the slender cone even at a large distance from the nosetip. The results of the calculations are compared with experimental data.     

Numerical simulation of pedestrian flow past a circular obstruction

In this paper, a revisiting Hughes' dynamic continuum model is used to investigate and predict the essential macroscopic characteristics of pedestrian flow, such as flow, density and average speed, in a two dimensional continuous walking facility scattered with a circular obstruction. It is assumed that pedestrians prefer to walk a path with the lowest instantaneous travel cost from origin to destination, under the consideration of the current traffic conditions and the tendency to avoid a high-density region and an obstruction. An algorithm for the pedestrian flow model is based on a cellcentered finite volume method for a scalar conservation law equation, a fast sweeping method for an Eikonal-type equation and a second-order TVD Runge-Kutta method for the time integration on unstructured meshes. Numerical results demonstrate the effectiveness of the algorithm. It is verified that density distribution of pedestrian flow is influenced by the position of the obstruction and the path-choice behavior of pedestrians.     

Supersonic viscous perfect-gas flow past a slender sharp elliptic cone

The supersonic M_∞ = 5 flow past slender elliptic cones with the semi-vertex angle in the plane of the major semi-axis ? _c = 4° and an isothermal surface is investigated under the assumption of the flow symmetry. Calculations on the basis of the time-dependent three-dimensional Navier-Stokes and Reynolds equations are carried out on the Reynolds number and angle of attack ranges 10⁴ ≤ Re ≤ 108 and 0 ≤ α ≤ 15° for cones with ellipticity coefficients 1/32 ≤ δ= b/a ≤ 1. The effect of the relevant parameters of the problem on the flowfield structure and the aerodynamic characteristics of the cones is demonstrated.     

Supersonic viscous perfect gas flow past a circular cylinder

The complete Navier-Stokes equations are used to calculate supersonic perfect gas flow past a circular isothermal cylinder by the method described in [1]. The effects of the Mach number M=2.5–10 and the Reynolds number Re=30-10⁵ on the flowfield structure and heat transfer to the cylinder wall are investigated. Special attention is paid to the study of the near wake and the local characteristics on the leeward side of the cylinder.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.6, pp. 107–115, November–December, 1993.     

水下亚声速细长锥型射弹超空泡流的数值计算方法

采用理想可压缩流体无旋定常流动及超空泡尾部Riabushinsky闭合方式假定,基于水动力学势流理论及细长体理论,建立了描述水下亚声速条件下细长锥型射弹超空泡流动的积分微分方程。发展了求解该方程的数值离散方法,提出多种超空泡外形初始解,分析了它们对超空泡形态计算结果的影响,优化了计算过程,简化了初始迭代条件。分析了流体压缩性对超空泡流动参数的影响,当马赫数大于0.3时,超空泡外形、射弹表面压力系数及射弹运动压差阻力系数均明显增大。计算得到的超空泡流动参数与相关文献的理论和实验结果吻合良好。     

Experiments on the flow past long circular cylinders in a shear flow

This paper describes an experimental investigation of the flow past circular cylinders, with the mean flow perpendicular to the cylinder axis, at conditions that yield a strong three-dimensional behaviour. The experiments were carried out in the subcritical regime. Long cylinders with end plates were subjected to shear flow with a linear velocity profile in the spanwise direction generated by means of a curved gauze. It was concluded that spanwise cellular structures of vortex shedding emerged in the wake, more clearly for some boundary conditions than others. These structures are characterised by a portion of spanwise length, a cell, having constant shedding frequency over a time average, which implies that there were no vortex dislocations inside that cell during that time. These features were studied using flow visualisation and hot-film anemometry. Spectra of the local shedding frequency are shown, revealing the effect of the shear parameter (=0.02 and 0.04) and aspect ratio L/D (=20.6 and 8) on the stability and geometry of the cells at several Reynolds numbers in the range of 3.13×10³Re_m1.25×10⁴.     

Supersonic axisymmetric flow past a blunt cone executing longitudinal low-frequency oscillations

The aerodynamic parameters of an oscillating cone in unsteady axisymmetric supersonic flow are investigated on the basis of the inviscid perfect gas model both in the absence and in the presence of strong air injection from its flat end into the shock layer.     

Supersonic flow past a sharp cone oscillating about a zero angle of attack

Supersonic perfect gas or equilibrium dissociated air flow past a sharp circular cone oscillating about a zero angle of attack is considered at small Strouhal numbers. The distribution of the gasdynamic parameters in the flow is found within the framework of the linear theory of finite-thickness bodies. The domain of the determining parameters for which the effect of equilibrium dissociation is substantial is found. The pitch moment coefficient related to the angular velocity of vibration is determined. Analytic expressions are derived for the gasdynamic characteristics at hypersonic flow velocities. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, pp. 124–136, November–December, 1998.