When needing to mix two fluids rapidly, turbulent flow can be beneficial. Onepoint statistics for turbulent wallbounded flows at reynolds numbers up to. An experimental investigation of the effects of convex curvature and freestream turbulence on momentum and heat transfer in a boundary introduction transition from laminar to turbulent boundary layer flow significantly increases local wall shear stress and convective heat transfer rates. While the impact of roughness on the meanvelocity profile of turbulent wall layers is well understood, at least qualitatively, the manner in which other features are affected, especially in the outer layer, has been. One aspect discusses the formation and evolution of coherent structures, such as counterrotating vortex pairs cvps and hairpins, observed in various transitional as well as turbulent flows. Effects of convex transverse curvature on wallbounded. Laminar turbulent patterning in plane couette flow. A fully developed compressible turbulent flow in a channel with a lower wavy wall and a upper plane wall is studied using large eddy simulation. Durbins method of elliptic relaxation is used to incorporate the wall effects into the governing equations without the. The effects of curvature on the turbulent boundary layer in flow past turbine blades. Predictive model for wallbounded turbulent flow science.
Roughness effects on wallbounded turbulent flows article pdf available in physics of fluids 2610 october 2014 with 3,247 reads how we measure reads. For flows in which resolution of the viscous sublayer is desired, a pdf near wall model is developed in which the generalized langevin model is combined with an exact model for viscous transport. Spectral derivation of the classic laws of wallbounded. The turbulent flow field is divided into an outer and an inner region. Jul 31, 2006 fouriers law, which forms the basis of most engineering prediction methods for the turbulent heat fluxes, is known to fail badly in capturing the effects of streamline curvature on the rate of heat transfer in turbulent shear flows. This research is motivated by the observation that the pod basis functions are only optimal for the flow for which they were created. Wall bounded turbulent dispersed multiphase flows occur in a variety of industrial, biological and environmental applications. Isolating curvature effects in computing wallbounded turbulent flows article in international journal of heat and fluid flow 226. Isolating curvature effects in computing wall bounded turbulent flows.
Transition to turbulence in wallbounded shear flows center. To study the effects of curvature on wall bounded turbulent flows, a simulation of curvedchannel flow was performed. A lowreynoldsnumber secondmoment closure without wall reflection redistribution terms is tested in wallbounded turbulent flows with streamline curvature. The kepsilon turbulence model and a variant of it, proposed to improve the calculation of flows with streamline curvature, are used in conjunction with a oneequation near wall model. On the sensitization of turbulence models to rotation and curvature. Similar improvements were obtained in previous investigations considering free flow phenomena 6. This is because it is only at surfaces that vorticity can actually be generated by an oncoming flow is suddenly brought to rest to satisfy the noslip condition. The influence of control on proper orthogonal decomposition. On the transition to turbulence of wall bounded flows in general, and plane couette flow in particular. Aiaa20010725 isolating curvature effects in computing wall bounded turbulent flows christopher l. Some of the earliest research in the field of turbulent wallbounded flows was purely. Kim, active turbulence control for drag reduction in wall bounded flows, j.
In fluid dynamics, the law of the wall also known as the logarithmic law of the wall states that the average velocity of a turbulent flow at a certain point is proportional to the logarithm of the distance from that point to the wall, or the boundary of the fluid region. A new simpler rotationcurvature correction method for. Oct 01, 2000 prediction of streamline curvature effects on wall bounded turbulent flows the turbulence model was previously shown to give good predictions for a fully developed channel flow, boundary layers in zero, adverse and favorable pressure gradients, plane and round jets, and flows with wall blowing and suction. Two direct numerical simulations of a model problem approximating axial flow. Curvature effect on compressible turbulent flow over a. Extended integral wallmodel for largeeddy simulations. Isolating curvature effects in computing wallbounded turbulent flows. Boundarylayer stability and transition, chapter 12. Introduction to turbulencewall bounded turbulent flows. In these conditions, singlebranch spirals could be observed, whereas rotation and curvature effects were sizable. Analysis of streamline curvature effects on wall bounded turbulent flows. Pressure and velocity fluctuations in wallbounded turbulent flows. An inviscid effective outer wall shape, undocumented in the experiment, is obtained by using an.
The turbulence model was previously shown to give good predictions for a fully developed channel flow, boundary layers in zero, adverse and favorable pressure gradients, plane and round. The effect of the curvature to these canonical turbulent pipe flows is then added to generate prandtls secondary motion of first kind. The impact of streamwise convex curvature on the supersonic. A lowreynoldsnumber secondmoment closure without wall reflection redistribution terms is tested in wall bounded turbulent flows with streamline curvature. The use of a test case with pressure gradient can complicate the analysis by making it difficult to isolate the effects of curvature from the.
We mainly attempt to deal with the curvature effect on compressible turbulent flow over the wavy wall. Fluids 21, 111703 2009 introduced and used a decoupling procedure based on the hilbert transformation applied to the filtered smallscale component of the fluctuating streamwise velocity. Streamline curvature effects on turbulent boundary layers. Effects of wall curvature on turbulence statistics nasaads. A spectral numerical method with about onemillion modes was employed, and no explicit subgrid scale model was used. The examples for model verification are a the flow over a backwardfacing step, b the flow in a curved duct, and c swirling flows. Some typical quantities including the mean turbulence statistics, dilatation and baroclinic terms in the enstrophy equation, turbulent kinetic. Aiaa 20010725 isolating curvature effects in computing. Gatski, title isolating curvature effects in computing wallbounded turbulent flows, year 2001 share. Convex and concave surface curvature effects in wall. A new scalar reynolds stress model for nonisothermal wall. For turbulent flows, however, and as a result of the complex nature of such flows, the more practical. Mvps are used to compute fluxes and other quantities of engineering interest, notably the turbulent friction which sets the power needed to operate a pipeline and the draining capacity. The effects of curvature on the turbulent boundary layer by v.
Pope 2000 h2d b z y flow a l z y c u 0 flow y rd r d b x x x figure 7. Gatski t nasa langley research center hampton, virginia abstract the flow over the zeropressuregradient somellor convex curved wall is simulated using the navierstokes equations. A threedimensional, timedependent, direct numerical simulation of lowreynolds number turbulent flow in a mildly curved channel was performed, and the results examined to determine the mechanism by which curvature affects wall bounded turbulent shear flows. The results show that, in general, roughness effects are confined to the inner layer.
This paper outlines the authors experimental research in rough wall bounded turbulent flows that has spanned the past 15 years. Recent experimental and direct numerical simulation data of twodimensional, isothermal wall bounded incompressible turbulent flows indicate that reynoldsnumber effects are not only present in the outer layer but are also quite noticeable in the inner layer. The effects of convex transverse curvature on the wall pressure fluctuations were studied through direct numerical simulations. An explicit algebraic model for turbulent heat transfer in. The current dataset will be useful for modelling particles advected in wall bounded turbulent flows where the effects of the curvature are not negligible. Lowreynoldsnumber, mildly curved, turbulent channel flow has been simulated by direct numerical solution of the navier stokes equations. An analysis of curvature effects for the control of wall. A phenomenological model to describe turbulent friction in.
Pdf methods are extended to include modeling of wall bounded turbulent flows. Pdf roughness effects on wallbounded turbulent flows. Their combined citations are counted only for the first article. Under the action of control, the pod basis may be significantly altered so. Comparison of four turbulence models for wallbounded flows. Mar 22, 2015 wall turbulent flows are constrained by the presence of at least one rigid wall, which imposes a noslip boundary condition at its surface. Yet even for one of the simplest, canonical casessmooth, pressuredriven channel flowtheir bulk properties have defied simplified theoretical explanation, relying predominantly on dimensional analysis or similarity arguments.
Analysis of streamline curvature effects on wall bounded turbulent flows application of turbulence models to separated flow over rough surfaces 1 june. Convex transverse curvature effects in wall bounded turbulent flows are significant if the boundarylayer thickness is large compared to the radius of curvature large. Dimensionless velocity data from a wide variety of turbulent duct and boundarylayer flows are shown here. The effect of convex surface curvature on turbulent. An analysis of the destabilizing curvature effects on the. Wallbounded turbulent flows are pervasive in a variety of domains, including the environment, biology, and industry. Contribution of reynolds stress distribution to the skin. Isolating curvature effects in computing wallbounded. Modeling turbulent flows introductory fluent training. When fluid flows past a solid object, the bulk of the turbulent motion is concentrated at the surface boundary, but it is unclear to what extent these inner motions are influenced by. In accordance with townsends reynolds number similarity hypothesis, the outer layer is insensitive to surface condition except in the role it plays in setting the length and.
Direct numerical simulation of turbulent incompressible planechannel flow between a smooth wall and one covered with regular threedimensional roughness elements is performed. Turbulence modeling is the construction and use of a mathematical model to predict the effects of turbulence. The flow over the zeropressuregradient somellor convex curved wall is simulated using the navierstokes equations. The one equation spalartallmaras sa turbulence model overpredicts eddy viscosity, and its boundary layer profiles are too full. The threedimensional timedependent incompressible navierstokes equations were solved in the domain bounded by sectors of concentric cylinders see figure 1 for a scale drawing of the domain. Prediction of streamline curvature effects on wall bounded turbulent flows article in international journal of heat and fluid flow 215. The effects of curvature in wallbounded turbulent flows journal of. Pdf convex and concave surface curvature effects in wall. The effects of curvature in wallbounded turbulent flows. May 17, 2012 longitudinal curvature effects in turbulent boundary layers progress in aerospace sciences, vol. Pdf on turbulent flows dominated by curvature effects. Analysis of streamline curvature effects on wallbounded.
Curvature effects in the laminar and turbulent freejet boundary. This article discusses the description of wallbounded turbulence as a deterministic. The probability density function of the wallshear stress pdf. The near wall behaviour of the nonlinear model for the pressurestrain correlation proposed by speziale, sarkar and gatski j. The oneequation spalartallmaras turbulence model overpredicts eddy viscosity, and its boundary layer profiles are too full. Vorticity flux control for a turbulent channel flow, phys. In this talk several aspects of transition to turbulence in wall bounded shear flows are addressed. An adjoint optimization method is utilized to design an inviscid outer wall shape required for a turbulent flow field solution of the somellor convex curved. Convex and concave surface curvature effects in wall bounded turbulent flows article pdf available in aiaa journal 296. Convex transverse curvature effects in wall bounded turbulent flows are significant if the boundary layer thickness is large compared to the radius of curvature.
A theoretical closure model for wall bounded turbulent flows. The new factor excludes the lagrangian derivative of the strain rate tensor that exists in the sarc model. Meanvelocity profile of smooth channel flow explained by a. Convex and concave surface curvature effects in wallbounded turbulent flows. Prediction of streamline curvature effects on wallbounded. Particleladen turbulent wallbounded flows in moderately. Turbulent flows are commonplace in most real life scenarios, including the flow of blood through the cardiovascular system, the airflow over an aircraft wing, the reentry of space vehicles, besides others.
Tropeayarinfoss, springer, 2007 whether objective is transition control, 3d, secondary instabilities, nonlinear effects, or receptivity, two rules must. An analysis of curvature effects for the control of wall bounded shear flows. The few applications of navierstokes codes to curved wallbounded flows have generally been for cases with substantial pressure gradients, such as the uduct test case of monson and seegmiller 1992. Flow facility design and experimental studies of wallbounded.
Convex and concave surface curvature effects in wallbounded. This flow regime is common in sonar devices towed by long cables. Coherent structures in wallbounded turbulence fluid dynamics. A sensitive scalar measure of the variation in pdf shapes is the kullback. Accurate presentation of the flow in the near wall region determines successful prediction of wall bounded turbulent flows. There, even the most energetic eddies are relatively small, on the order of in fact, because the turbulent energy in a wall bounded flow is typically supplied by the wall, there can exist a reverse energy cascade, from small to large scales. Modeling reynoldsnumber effects in wallbounded turbulent. The response of a welldeveloped turbulent boundary layer to suddenly applied convex surface curvature is investigated, using conditionalsampling techniques so that the turbulent and non turbulent regions of the flow can be clearly distinguished. Using this wall shape with a navierstokes method, the abilities of various turbulence models to simulate the effects of curvature without the complicating factor of streamwise pressure gradient can be evaluated. The inner region is made up of a loglaw region and a wall layer. Prediction of streamline curvature effects on wall bounded turbulent flows the turbulence model was previously shown to give good predictions for a fully developed channel flow, boundary layers in zero, adverse and favorable pressure gradients, plane and round jets, and flows with wall. Preliminary measurements in the turbulent boundary layers on a circular cylinder and the convex wall of a 90 degree curved duct are described.
The wall layer is viewed in terms of the well known inrushsweepburst sequence observed since 1967. The effects of curvature in wallbounded turbulent flows volume 175 robert d. Curvature effects in the laminar and turbulent freejet. Reynolds number effects in wallbounded turbulent flows. The meanvelocity profile mvp of a wall bounded turbulent flow is the function uy that gives the mean timeaveraged velocity of the flow, u, at any given distance to the wall, y. Convex and concave surface curvature effects in wall bounded turbulent flows. However, in most cases, the churning and tumbling motions of a fluid during turbulent flow reduce the efficiency of a device or process. Pdf the effects of curvature on the turbulent boundary layer in. Turbulent flow close to solid walls is dominated by an ensemble of fluctuations of large and small spatial scales. Pdf flow past a representative low pressure lp turbine blade t106a has been. The performance of the method is examined through computations of fully developed curved duct flow and boundary layers on curved surfaces. Pdf this paper outlines the authors experimental research in roughwall bounded turbulent flows that has spanned the past 15 years. A new and much simpler rotation and curvature effects factor, which takes the form of richardson number suggested by hellsten originally for sst k.
Isolating curvature effects in computing wall bounded turbulent flows christopher lockwood rumsey, thomas b. The first and secondorder moments of the velocity and acceleration of the particulate phase in the same configurations are addressed in a companion paper by the same authors. Isolating curvature effects in computing wall bounded turbulent flows author. Patel cambridge university engineering department reports and memoranda no. The flow regime of interest is characterized by large ratio of the shearlayer thickness to the radius of curvature. Contribution of reynolds stress distribution to the skin friction in wall bounded flows.1552 214 1099 212 183 697 927 1434 261 180 682 1580 1409 448 482 699 1021 118 23 1604 1217 340 454 119 1408 1442 702 430 414 149 709 167 1113 406 1606 404 791 642 23 387 309 833 382 95 142 220 1361