INCREASING PROPERTY OF SPECTRUM IN THE VIBRATIONS OF A CYCLIC CHAIN OF MASSES DISTRIBUTED ACCORDING TO THE GTM SEQUENCE

ＩＮＣＲＥＡＳＩＮＧＰＲＯＰＥＲＴＹＯＦＳＰＥＣＴＲＵＭＩＮＴＨＥＶＩＢＲＡＴＩＯＮＳＯＦＡＣＹＣＬＩＣＣＨＡＩＮＯＦＭＡＳＳＥＳＤＩＳＴＲＩＢＵＴＥＤＡＣＣＯＲＤＩＮＧＴＯＴＨＥＧＴＭＳＥＱＵＥＮＣＥＳｈａｎｇＰｅｎｇｊｉａｎ（商朋见）（Ｄｅｐａｒ...     

ASYMPTOTIC ANALYSIS OF A CLASS OF NONLINEAR OSCILLATION EQUATION IN ELECTRICAL ENGINEERING

ＡＳＹＭＰＴＯＴＩＣＡＮＡＬＹＳＩＳＯＦＡＣＬＡＳＳＯＦＮＯＮＬＩＮＥＡＲＯＳＣＩＬＬＡＴＩＯＮＥＱＵＡＴＩＯＮＩＮＥＬＥＣＴＲＩＣＡＬＥＮＧＩＮＥＥＲＩＮＧＣｈｅｎｇＹｏｕ－ｌｉａｎｇ（程友良）（ＤｅｐａｒｔｍｅｎｔｏｆＦｕｎｄａｍｅｎｔａｌＣｏｕ...     

THE EXISTENCE OF PERIODIC SOLUTION OF THE FOURTH ORDINARY NONLINEAR DIFFERENTIAL EQUATION CAUSED BY FLOW－IN

ＴＨＥＥＸＩＳＴＥＮＣＥＯＦＰＥＲＩＯＤＩＣＳＯＬＵＴＩＯＮＯＦＴＨＥＦＯＵＲＴＨＯＲＤＩＮＡＲＹＮＯＮＬＩＮＥＡＲＤＩＦＦＥＲＥＮＴＩＡＬＥＱＵＡＴＩＯＮＣＡＵＳＥＤＢＹＦＬＯＷ－ＩＮＤＵＣＥＤＶＩＢＲＡＴＩＯＮＧｕＱｉｎｇ－ｆａｎｇ（顾清芳）Ｔａ...     

ANALYTICAL SOLUTION OF RADIATED SOUND PRESSURE OF RING－STIFFENED CYLINDRICAL SHELLS IN FLUID MEDIUM

ＡＮＡＬＹＴＩＣＡＬＳＯＬＵＴＩＯＮＯＦＲＡＤＩＡＴＥＤＳＯＵＮＤＰＲＥＳＳＵＲＥＯＦＲＩＮＧ－ＳＴＩＦＦＥＮＥＤＣＹＬＩＮＤＲＩＣＡＬＳＨＥＬＬＳＩＮＦＬＵＩＤＭＥＤＩＵＭＸｉｅＧｕａｎｍｏ（谢官员模）ＬｕｏＤｏｎｇｐｉｎｇ（骆东平）（Ｒｅｃｅｉｖ...     

STRESS－STBAIN FIELD NEAR CRACK TIP AND CALCULATION OF CRITICAL STRESS OF CRACK PROPAGATION IN A PURE BENDING BEAM OF RECTANGULAR SECTION WITH ONE－SIDED MODEICRACK

ＳＴＲＥＳＳ－ＳＴＢＡＩＮＦＩＥＬＤＮＥＡＲＣＲＡＣＫＴＩＰＡＮＤＣＡＬＣＵＬＡＴＩＯＮＯＦＣＲＩＴＩＣＡＬＳＴＲＥＳＳＯＦＣＲＡＣＫＰＲＯＰＡＧＡＴＩＯＮＩＮＡＰＵＲＥＢＥＮＤＩＮＧＢＥＡＭＯＦＲＥＣＴＡＮＧＵＬＡＲＳＥＣＴＩＯＮＷＩＴＨＯＮＥ－Ｓ...     

NOETHER’S CONSERVATION LAWS OF HOLONOMIC NONCONSERVATIVE DYNAMICAL SYSTEMS IN GENERALIZED MECHANICS

ＮＯＥＴＨＥＲ’ＳＣＯＮＳＥＲＶＡＴＩＯＮＬＡＷＳＯＦＨＯＬＯＮＯＭＩＣＮＯＮＣＯＮＳＥＲＶＡＴＩＶＥＤＹＮＡＭＩＣＡＬＳＹＳＴＥＭＳＩＮＧＥＮＥＲＡＬＩＺＥＤＭＥＣＨＡＮＩＣＳＱｉａｏＹｏｎｇ－ｆｅｎ（乔永芬）ＹｕｅＱｉｎｇ－ｗｅｎ（岳庆文）（Ｎｏ...     

CONSTRUCTION OF MODIFIED TAYLOR－GALERKIN FINITE ELEMENTS AND ITS APPLICATION IN COMPRESSIBLE FLOW COMPUTATION

ＣＯＮＳＴＲＵＣＴＩＯＮＯＦＭＯＤＩＦＩＥＤＴＡＹＬＯＲ－ＧＡＬＥＲＫＩＮＦＩＮＩＴＥＥＬＥＭＥＮＴＳＡＮＤＩＴＳＡＰＰＬＩＣＡＴＩＯＮＩＮＣＯＭＰＲＥＳＳＩＢＬＥＦＬＯＷＣＯＭＰＵＴＡＴＩＯＮＣＯＮＳＴＲＵＣＴＩＯＮＯＦＭＯＤＩＦＩＥＤＴＡＹＬＯＲ...     

UNCONDITIONAL STABLE SOLUTIONS OF THE EULER EQUATIONS FOR TWO－AND THREE－D WINGS IN ARBITRARY MOTION

ＵＮＣＯＮＤＩＴＩＯＮＡＬＳＴＡＢＬＥＳＯＬＵＴＩＯＮＳＯＦＴＨＥＥＵＬＥＲＥＱＵＡＴＩＯＮＳＦＯＲＴＷＯ－ＡＮＤＴＨＲＥＥ－ＤＷＩＮＧＳＩＮＡＲＢＩＴＲＡＲＹＭＯＴＩＯＮＧａｏＺｈｅｎｇｈｏｎｇ（高正红）（ＲｅｃｅｉｖｅｄＪａｎ．１２,１９９５,Ｃ...     

EXISTENCE THEOREMS OF SOLUTIONS FOR TWO－POINT BOUNDARY VALUE PROBLEM OF SECOND ORDER ORDINARY DIFFERENTIAL EQUATIONS IN BANACH SPACES

ＥＸＩＳＴＥＮＣＥＴＨＥＯＲＥＭＳＯＦＳＯＬＵＴＩＯＮＳＦＯＲＴＷＯ－ＰＯＩＮＴＢＯＵＮＤＡＲＹＶＡＬＵＥＰＲＯＢＬＥＭＯＦＳＥＣＯＮＤＯＲＤＥＲＯＲＤＩＮＡＲＹＤＩＦＦＥＲＥＮＴＩＡＬＥＱＵＡＴＩＯＮＳＩＮＢＡＮＡＣＨＳＰＡＣＥＳＺｈａｎｇＳｈｉｓ...     

DYNAMIC RESPONSE OF LAMINATED ORTHOTROPIC SPHERICAL SHELLSINCLUDING TRANSVERSE SHEAR DEFORMATION AND ROTATORY INERTIA

（杨宜谦）（马和中）（王俊奎）ＤＹＮＡＭＩＣＲＥＳＰＯＮＳＥＯＦＬＡＭＩＮＡＴＥＤＯＲＴＨＯＴＲＯＰＩＣＳＰＨＥＲＩＣＡＬＳＨＥＬＬＳＩＮＣＬＵＤＩＮＧＴＲＡＮＳＶＥＲＳＥＳＨＥＡＲＤＥＦＯＲＭＡＴＩＯＮＡＮＤＲＯＴＡＴＯＲＹＩＮＥＲＴＩＡ￥Ｙａｎｇ...     

Three-dimensional boundary-layer equations in regions with large pressure gradient

Assuming that in regions with large pressure gradient the flow parameters in a direction perpendicular to the pressure gradient change little in comparison with changes along the pressure gradient, we show that the calculation of the three-dimensional boundary layer may be reduced to the integration of equations analogous to the two-dimensional boundary-layer equations along curves tangent to the pressure gradient.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 49–55, September–October, 1971.     

Bulk flow parameters in turbulent wall boundary layers near separation

Experiments were conducted in a turbulent boundary layer near separation along a flat plate. The pressure gradient in flow direction was varied such that three significant boundary layer configurations could be maintained. The flow in the test section thus had simultaneously a region of favourable pressure gradient, a region of strong adverse pressure gradient with boundary layer separation and a region of reattached boundary layer. Specially designed fine probes facilitated the measurements of skin friction and velocity distribution very close to the wall. Bulk flow parameters such as skin friction coefficient C _f, Reynold's number Re_δ2 and shape factors H and G, which are significant characteristics of wall boundary layers were evaluated. The dependence of these parameters on the Reynolds number and along the test section was explored and the values were compared with other empirical and analytical formulae known in the literature.     

DNS of heat transfer in transitional, accelerated boundary layer flow over a flat plate affected by free-stream fluctuations

Direct numerical simulations (DNS) of flow over and heat transfer from a flat plate affected by free-stream fluctuations were performed. A contoured upper wall was employed to generate a favourable streamwise pressure gradient along a large portion of the flat plate. The free-stream fluctuations originated from a separate LES of isotropic turbulence in a box. In the laminar portions of the accelerating boundary layer flow the formation of streaks was observed to induce an increase in heat transfer by the exchange of hot fluid near the surface of the plate and cold fluid from the free-stream. In the regions where the streamwise pressure gradient was only mildly favourable, intermittent turbulent spots were detected which relaminarised downstream as the streamwise pressure gradient became stronger. The relaminarisation of the turbulent spots was reflected by a slight decrease in the friction coefficient, which converged to its laminar value in the region where the streamwise pressure gradient was strongest.     

Wake layer in a thermal turbulent boundary layer with pressure gradient

The open equations of thermal turbulent boundary layer subjected to pressure gradient have been analysed by method of matched asymptotic expansions at large Reynolds number. The flow is divided into outer wake layer and inner wall layer. The asymptotic expansions are matched by Millikan-Kolmogorov hypothesis. The temperature profile in overlap region yields composite law which reduce to log. law for moderate pressure gradient and inverse half power law for strong adverse pressure gradient. In case of a shallow thermal wake, the matching result of outer wake layer reduces to composite temperature defect law, which is more general than the classical log. law. The comparison of data for thermal boundary layer with strong adverse pressure gradient is also considered. Received on 26 May 1998     

压力梯度对边界层两相流动稳定性的影响

分析了有压力梯度的边界层两相流动稳定性,推导出类似于Saffman理论的修正的稳定性方程,数值计算采用高精度的谱方法。结果说明,压力梯度对边界层两相流动稳定性有显著的影响,顺压梯度增强流动稳定性,而逆压梯度则促进流动失稳。在不同的压力梯度和浓度下,Stokes数对流动稳定性的影响是一致的,存在一个临界Stokes数,小Stokes数促进流动失稳,而大Stokes数则提高临界雷诺数,抑制流动失稳的最佳Stokes数为10的量级。     

Mechanism of compressor airfoil boundary layer flow control using nanosecond plasma actuation

The flow control effects of nanosecond plasma actuation on the boundary layer flow of a typical compressor controlled diffusion airfoil are investigated using large eddy simulation method. Three types of plasma actuation are designed to control the boundary layer flow, and two mechanisms of compressor airfoil boundary layer flow control using nanosecond plasma actuation have been found. The plasma actuations located within the laminar boundary layer flow can induce a small vortex structure through influencing on the density and pressure of the flow field. As the small vortex structure moves downstream along the blade surface with the main flow, it can suppress the turbulent flow mixing and reduce the total pressure loss. The flow control effect of the small vortex structure is summarized as wall jet effect. Differently, the plasma actuation located within the turbulent boundary layer flow can act on the shear layer flow and induce a large vortex structure. While moving downstream, this large vortex structure can suppress the turbulent flow mixing too.     

Reynolds Stress Budgets in Couette and Boundary Layer Flows

Reynolds stress budgets for both Couette and boundary layer flows are evaluated and presented. Data are taken from direct numerical simulations of rotating and non-rotating plane turbulent Couette flow and turbulent boundary layer with and without adverse pressure gradient. Comparison of the total shear stress for the two types of flows suggests that the Couette case may be regarded as the high Reynolds number limit for the boundary layer flow close to the wall. The limit values of turbulence statistics close to the wall for the boundary layer for increasing Reynolds number approach the corresponding Couette flow values. The direction of rotation is chosen so that it has a stabilizing effect, whereas the adverse pressure gradient is destabilizing. The pressure-strain rate tensor in the Couette flow case is presented for a split into slow, rapid and Stokes terms. Most of the influence from rotation is located to the region close to the wall, and both the slow and rapid parts are affected. The anisotropy for the boundary layer decreases for higher Reynolds number, reflecting the larger separation of scales, and becomes close to that for Couette flow. The adverse pressure gradient has a strong weakening effect on the anisotropy. All of the data presented here are available on the web [36]. This revised version was published online in July 2006 with corrections to the Cover Date.     

DNS of a Laminar Separation Bubble in the Presence of Oscillating External Flow

A three-dimensional Direct Numerical Simulation (DNS) of a laminar separation bubble in the presence of oscillating flow is performed. The oscillating flow induces a streamwise pressure gradient varying in time. The special shape of the upper boundary of the computational domain, together with the oscillating pressure gradient causes the boundary layer flow to alternately separate and re-attach. When the inflow decelerates, the shear layer starts to separate and rolls up. Simultaneously the flow becomes 3D. After a transient period, the phase-averaged reverse flow inside the separation bubble reaches speeds ranging from 20 up to 150% of the free-stream velocity. During these phases, the flow is absolutely unstable and self-sustained turbulence can exist. When the inflow starts to accelerate, a spanwise roll of turbulent flow is shed from the shear layer. Shortly after this, the remainder of the separation bubble moves downstream and rejoins with the shed turbulent roll. During the flow-acceleration phase, a patch of laminar boundary layer flow is obtained. Along the flat plate, a series of turbulent patches of flow travelling downstream, separated by laminar flow can be observed, reminiscent of boundary layer flow in a turbine cascade with periodically appearing free-stream disturbances.     

Effect of Streamline Curvature on Three-Dimensionality of Transitional Near-Wall Flow in a Linear Hydrofoil Cascade: A DNS Investigation

Flow, Turbulence and Combustion - The laminar flow on a curved surface transits to turbulent induced by streamline curvature which generates pressure gradient field and separated shear layer flow....     

Wake-boundary layer interaction subject to convex and concave curvatures and adverse pressure gradient

Measurements of mean velocity and turbulent quantities have been carried out when the wake of a symmetrical airfoil interacts with the boundary layer on the (i) walls of a straight duct/diffuser and (ii) convex and concave walls of a curved duct/diffuser. The effects of adverse pressure gradient and of curvatures on the interaction are studied separately and in combination. Six cases are considered, viz. with (i) neither pressure gradient nor curvature, (ii) adverse pressure gradient and no curvature, (iii) and (iv) convex curvature with zero and adverse pressure gradients, respectively, (v) and (vi) concave curvature with zero and adverse pressure gradients, respectively. For the flows with curvature, the curvature parameter δ/R is 0.023, and for the flows with adverse pressure gradient, the Clauser pressure gradient parameter β is 0.62. The individual influences of adverse pressure gradient and convex and concave curvatures on the boundary layer are similar to those observed by earlier investigations. It is further observed that the combined effect of concave/convex curvature and the adverse pressure gradient causes higher turbulence intensities than the sum of the individual effects. The effect of curvature is to make the wake asymmetric, and in combination with adverse pressure gradient the asymmetry increases. It is observed that the adverse pressure gradient causes faster wake–boundary-layer interaction. Comparing measurements in a straight duct, a curved duct, a curved diffuser and a straight diffuser, it is seen that the convex curvature reduces the boundary layer thickness. The asymmetry in wake development compensates for this effect and the wake–boundary-layer interaction on a convex surface is almost the same as that on a straight surface. In the case of interaction with the boundary layer on a concave surface, the curvature increases the boundary layer thickness and causes enhanced turbulence intensities. However, the asymmetry in wake is such that the extent of wake is lower towards the boundary layer side. As a result, the wake–boundary-layer interaction on concave surface is almost the same as on a straight surface. The interaction is faster in the presence of adverse pressure gradient. Received: 16 June 2000 / Accepted: 17 May 2001