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Peter R.n. Childs - One of the best experts on this subject based on the ideXlab platform.
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Rotor-Stator Disc Cavity Flow
Rotating Flow, 2020Co-Authors: Peter R.n. ChildsAbstract:A rotating Disc adjacent to a Stationary Disc forms a cavity known as a rotor-stator cavity or wheelspace. The proximity of the Discs, flow conditions around the periphery, and flow supplied to the cavity all have a significant influence on the conditions in the cavity. This chapter provides an overview of the flow associated with a single Disc rotating with proximity to a Stationary casing. The flow structures are typically nontrivial with complex interactions and different behavior, depending on whether the Disc boundary layers are separate, the presence of a shroud at the outer periphery, and the supply or extraction of fluid from the cavity. Design-oriented correlations for bulk parameters such as boundary layer thickness, mass flow, and moment coefficients have been presented for most of the geometrical conditions considered. The insight resulting from the descriptions, along with the correlations, provide a basis for modeling Disc flows, undertaking preliminary design calculations, and validating CFD models.
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Introduction to Rotating Disc Systems
Rotating Flow, 2020Co-Authors: Peter R.n. ChildsAbstract:Rotating Discs are found in a range of engineering applications such as gas turbine engines, flywheels, gears, and brakes. This chapter considers the subject of a plain rotating Disc in detail, thereby providing an in-depth development of understanding of the flow physics and modeling approach for both laminar and turbulent flow. It presents an overview of the flow associated with isolated rotating Discs and rotating fluids near a surface. It provides the design orientated correlations for bulk parameters such as boundary layer thickness, mass flow, and moment coefficients. The insight resulting from the descriptions, along with the correlations, provide a basis for modeling Disc flows and undertaking preliminary design calculations. Flow over an isolated rotating Disc can be used as a starting point for analysis of flow in a rotor-stator Disc system where a Disc rotates in close proximity to a Stationary Disc. The flow associated with Discs is important in a number of applications ranging from Disc drives for the memories of computers and electronic products to automotive Discs brakes, flywheels, cutting Discs, gear wheels, and Discs to support turbomachinery blades. Shear stresses between the Disc and the fluid in which it is rotating dictate the power required to drive the Disc to overcome frictional drag, and the local flow field will influence the heat transfer. Unfortunately, a number of factors combine to frustrate any universal analysis, and the flow conditions and the proximity of local geometry need to be taken into account.
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Flow in rotating components - Discs, cylinders and cavities
2007Co-Authors: Peter R.n. ChildsAbstract:This Data Item introduces the subject of flow in applications where rotating machinery components induceflow rotation. There are many examples of rotating and swirling flow in engineering such as the flowbetween a Stationary Disc and a rotating Disc, in a gas turbine engine or turbocharger, and the flow in anannulus with a rotating inner cylinder, between the armature and stator of an electric motor. The aim of this Data Item is to introduce the phenomena involved in rotating flows and to provide the readerwith guidance and techniques for modelling specific rotating flow applications. The flow applicationsconsidered in this Data Item relate to Disc and cylindrical geometries, i.e. rotating Discs, cylinders andcavities, predominantly in steady-state, stable flow conditions. The correlations provided are based onanalytical, experimental and computational fluid dynamics (CFD) modelling of the flow and can be usedin parametric design studies and optimisation.
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Prediction of ingress rates to turbine and compressor wheelspaces
International Journal of Heat and Fluid Flow, 1997Co-Authors: F J Bayley, Peter R.n. ChildsAbstract:Abstract The paper uses the inviscid form of the momentum equation for rotating flows to analyse conditions in the space between a rotating and Stationary Disc—the “wheelspace”. Its principal object is to predict the ingress from the external atmosphere when the imposed rate of radial flow to the wheelspace is less than required to suppressed inflow. The analysis developed can deal with a varying external pressure along the seal, a situation now known to have a profound effect upon the amount of ingress. The inviscid assumption inevitably requires an empirical input, and critical parameters in determining sealing performance appear as the local ratio of the tangential fluid velocity in the wheelspace to that of the rotating Disc and the seal inflow and outflow Discharge coefficients. Although the former of these appears to be strongly dependent upon rate of imposed flow, rational values for these critical coefficients yield results in good agreement with experimental observation from test rigs simulating turbomachine stages. There is a need to build a database of such empirical coefficients for the use of system designers from a large amount of performance data from many designs of seal.
Brian Launder - One of the best experts on this subject based on the ideXlab platform.
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Studies of Transitional and Turbulent Flows in Rotor-Stator Cavity Using High-Performance Computations
Direct and Large-Eddy Simulation V, 2020Co-Authors: Eric Serre, Patrick Bontoux, Brian LaunderAbstract:In this paper, flows confined between a rotating and a Stationary Disc are investigated using direct numerical simulation based on a pseudo-spectral method. The structure of these flows is very complex involving laminar, transitional and turbulent flow regions and moreover the turbulence is strongly inhomogeneous and anisotropic. Consequently, these flows are very challenging for the turbulence modellers. The present contribution extends the direct numerical simulations (DNS) from the transitional into the turbulent flow regime. In this work, two cases of flow are studied in annular cavities of aspect ratios L(= R/H)=2.35 and L=4.72. Our work aims at using DNS as a tool for turbulence research. The instantaneous quantities have been analysed and the results have been averaged so as to provide target turbulence data for any subsequent modelling attempts at reproducing the flow.
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Transitional–turbulent flow with heat transfer in a closed rotor–stator cavity
Journal of Turbulence, 2004Co-Authors: Eric Serre, Patrick Bontoux, Brian LaunderAbstract:In this paper, a non-isothermal flow confined between a rotating and a Stationary Disc is investigated using direct numerical simulation. Besides its fundamental importance as a three-dimensional prototype flow, such flows arise in many industrial devices, especially in turbomachinery applications. Our aim is to include the effects of density variation as this introduces a quasi-buoyant effect on the near-wall layers due to the radial acceleration, Ω2 r. None of the detailed experimental studies of Disc-cavity flows has examined this effect due to the extreme flow conditions arising in an actual gas turbine. As a preliminary exploration we show here the effects on the mean flow of Rayleigh numbers up to 2 × 106. The direct numerical simulation is performed by integrating the time-dependent Navier–Stokes equations with a three-dimensional spectral method. The Boussinesq approximation is used to take into account the centrifugal-buoyancy effects. The effects of thermal convection have been examined for a tr...
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Direct Numerical Simulation of Transitional Turbulent Flow in a Closed Rotor-Stator Cavity
Flow Turbulence and Combustion, 2002Co-Authors: E. Serre, P. Bontoux, Brian LaunderAbstract:The transitional turbulent regime in confined flow between a rotating and a Stationary Disc is studied using direct numerical simulation. Besides its fundamental importance as a three-dimensional prototype flow, such flows frequently arise in many industrial devices, especially in turbomachinary applications. The present contribution extends the DNS simulation into the turbulent flow regime, to a rotational Reynolds number Re =3 × 10^5. An annular rotor-stator cavity of radial extension Δ R and height H , is considered with L = 4.72( L = Δ R / H ) and Rm = 2.33 ( Rm = ( R _1+ R _0)/Δ R ). The direct numerical simulation is performed by integrating the time-dependent Navier–Stokes equations until a statistically steady state is reached. A three-dimensional spectral method is used with the aim of providing both very accurate instantaneous fields and reliable statistical data. The instantaneous quantities are analysed in order to enhance our knowledge of the physics of turbulent rotating flows. Also, the results have been averaged so as to provide target turbulence data for any subsequent modelling attempts at reproducing the flow.
Roger Debuchy - One of the best experts on this subject based on the ideXlab platform.
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On the Flow Behavior in Rotor-Stator System with Superposed Flow
International Journal of Rotating Machinery, 2008Co-Authors: Roger Debuchy, Fadi Abdel Nour, Gérard BoisAbstract:The flow between a rotor and a stator at high Reynolds number and small Ekman number is divided into three domains, two boundary layers adjacent to the Discs separated by a central core. In the present work, a simple theoretical approach provides analytical solutions for the radial distribution of the core swirl ratio valid for a rotor-stator system with a superposed radial inflow rate. At first, the flow in the rotor boundary layer is assumed to behave as expressed by Owen and Rogers (1989) in the case of a turbulent flow on a rotating single Disc. On the stator side, a necessary compensation flow rate must take place according to the conservation of mass. It is found that this compensation flow rate cannot be estimated with a good accuracy using the hypotheses of a Stationary Disc in a rotating fluid by Owen and Rogers (1989). Thus, two innovative weighting functions are tested, leading to new analytical laws relating the core swirl ratio K to the coefficient of flow rate Cqr introduced by Poncet et al. (2005). The adequacy between the theoretical solutions and numerous results of the literature is clearly improved and the Discussion allows a better understanding of the flow behavior.
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Heat transfer in a rotor-stator system with a radial inflow
European Journal of Mechanics B-fluids, 2001Co-Authors: Marc Djaoui, A Dyment, Roger DebuchyAbstract:Abstract The object of the present work is to produce a better understanding of the flow and heat transfer process occurring in a rotor-stator system, with a low aspect ratio and subjected to a superposed radial inflow. The theoretical approach presented in a previous paper (Debuchy et al., Eur. J. Mech. B-Fluids 17 (6) (1998) 791–810) in the framework of laminar, steady, axisymmetric flow is extended to heat transfer effects. The asymptotic model is simplified and new integral relations including temperature are indicated. The experiments, made in a rotor–stator system with a heated Stationary Disc, are in agreement with the features of the model in the explored range of the gap ratio, Ekman and Rossby numbers. The data include radial and circumferential mean velocity components, air temperature inside the cavity, temperature and temperature-velocity correlations, and also local Nusselt numbers measured on the Stationary Disc. The flow structure near the axis is found to be strongly affected by the presence of a superposed inflow, as already observed under isothermal conditions. By contrast, the mean temperature, as well as the correlations concerning velocity and temperature are smaller when a radial inflow is assigned.
Eric Serre - One of the best experts on this subject based on the ideXlab platform.
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Studies of Transitional and Turbulent Flows in Rotor-Stator Cavity Using High-Performance Computations
Direct and Large-Eddy Simulation V, 2020Co-Authors: Eric Serre, Patrick Bontoux, Brian LaunderAbstract:In this paper, flows confined between a rotating and a Stationary Disc are investigated using direct numerical simulation based on a pseudo-spectral method. The structure of these flows is very complex involving laminar, transitional and turbulent flow regions and moreover the turbulence is strongly inhomogeneous and anisotropic. Consequently, these flows are very challenging for the turbulence modellers. The present contribution extends the direct numerical simulations (DNS) from the transitional into the turbulent flow regime. In this work, two cases of flow are studied in annular cavities of aspect ratios L(= R/H)=2.35 and L=4.72. Our work aims at using DNS as a tool for turbulence research. The instantaneous quantities have been analysed and the results have been averaged so as to provide target turbulence data for any subsequent modelling attempts at reproducing the flow.
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Transitional–turbulent flow with heat transfer in a closed rotor–stator cavity
Journal of Turbulence, 2004Co-Authors: Eric Serre, Patrick Bontoux, Brian LaunderAbstract:In this paper, a non-isothermal flow confined between a rotating and a Stationary Disc is investigated using direct numerical simulation. Besides its fundamental importance as a three-dimensional prototype flow, such flows arise in many industrial devices, especially in turbomachinery applications. Our aim is to include the effects of density variation as this introduces a quasi-buoyant effect on the near-wall layers due to the radial acceleration, Ω2 r. None of the detailed experimental studies of Disc-cavity flows has examined this effect due to the extreme flow conditions arising in an actual gas turbine. As a preliminary exploration we show here the effects on the mean flow of Rayleigh numbers up to 2 × 106. The direct numerical simulation is performed by integrating the time-dependent Navier–Stokes equations with a three-dimensional spectral method. The Boussinesq approximation is used to take into account the centrifugal-buoyancy effects. The effects of thermal convection have been examined for a tr...
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on the nature of the boundary layers instabilities in a flow between a rotating and a Stationary Disc
Comptes Rendus Mecanique, 2002Co-Authors: Ewa Tuliskasznitko, Eric Serre, Patrick BontouxAbstract:Both theoretical linear stability analysis and direct numerical simulation are performed to study the transition flow between a Stationary and a rotating Disc. This paper concerns three- dimensional spiral and annular patterns computed with a high-order (spectral) numerical method and related to Bodewadt layer instabilities. The characteristic parameters of these boundary layer patterns are compared to the theoretical results and interpreted in terms of type I and type II generic instabilities. Moreover, the absolute instability regions are also theoretically identified and the critical Reynolds numbers of the convective/absolute transition in both layers are given. To cite this article: E. Tuliska-Sznitko et al., C. R. Mecanique 330 (2002) 91-99. 2002 Academie des sciences/Editions scientifiques et medicales Elsevier SAS fluid mechanics / instability and transition in rotating flows / convective and absolute instability / direct numerical simulation / linear stability analysis
H P Gail - One of the best experts on this subject based on the ideXlab platform.
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radial mixing in protoplanetary accretion disks i Stationary Disc models with annealing and carbon combustion
Astronomy and Astrophysics, 2001Co-Authors: H P GailAbstract:The interplay between radial mixing process in protoplanetary accretion Discs with processes leading to destruction or modication of the extinction properties of abundant dust species has signicant consequences for the properties of the disk. This paper studies the consequences of annealing amorphous silicate dust at T 800 K, of combustion of the carbon dust component at about T 1000 K and of mixing the products into cold outer Disc regions out to 10 AU and beyond. A model calculation in the one-zone approximation for Stationary Keplerian -disks around a solar-like protostar is combined with a solution of the equations for annealing of silicate dust grains, for carbon dust oxidation, and a solution of the diusion equations for radial mixing of the dust components in the Disc by turbulent flows. It is shown that annealing of amorphous silicate dust reduces the mass extinction coecient of the Disc matter by more than an order of magnitude in the warm Disc zone. Radial mixing of the freshly produced crystalline silicate dust into outer Disc regions reduces the opacity of the Disc material also in cold Disc regions where annealing is not possible. Mixing of carbon dust free material from the zone of carbon combustion into outer Disc regions also leads to a considerable reduction of the opacity of the Disc material. Radial mixing processes then modify the dust composition of the outer Disc regions and by means of the dependence of the disk properties (midplane temperature Tc ,v iscosity , . ..) on the opacity also modify the structure and evolution of a protoplanetary Disc. It is shown that turbulent mixing processes in the protoplanetary accretion Disc of a Solar System like system during its evolution prior to the onset of the formation of planetary bodies carry material from inner Disc regions r< 1 AU outwards to at least 10. . . 20 AU. This oers a simple explanation of the ndings that a signicant fraction of the cometary silicate dust grains are crystallised and that the matrix material of primitive meteorites contains thermally processed crystalline dust material.