Review of fluid flow and convective heat transfer within rotating disk cavities with impinging jet

International audienceFluid flow and convective heat transfer in rotor-stator configurations, which are of great importance in different engineering applications, are treated in details in this review. The review focuses on convective heat transfer in predominantly outward air flow in the rotor-stator geometries with and without impinging jets and incorporates two main parts, namely, experimental / theoretical methodologies and geometries/results. Experimental methodologies include naphthalene sublimation techniques, steadystate (thin layer) and transient (thermochromic liquid crystals) thermal measurements, thermocouples and infra-red cameras, hot-wire anemometry, laser Doppler and particle image velocimetry, laser plane and smoke generator. Theoretical approaches incorporate modern CFD computational tools (DNS, LES, RANS etc). Geometries and results part being mentioned starting from simple to complex elucidates cases of a free rotating disk, a single disk in the crossflow, single jets impinging onto stationary and rotating disk, rotor-stator systems without and with impinging single jets, as well as multiple jets. Conclusions to the review outline perspectives of the further extension of the investigations of different kinds of the rotor-stator systems and their applications in engineering practice

Aeronautical Engineering. A continuing bibliography with indexes, supplement 136, June 1981

This bibliography lists 424 reports, articles, and other documents introduced into the NASA scientific and technical information system in May 1981

Turbulence modeling of the Von Karman flow: viscous and inertial stirrings

International audienceThe present work considers the turbulent Von Karman flow generated by two counter-rotating smooth flat (viscous stirring) or bladed (inertial stirring) disks. Numerical predictions based on one-point statistical modeling using a low Reynolds number second-order full stress transport closure (RSM model) are compared to velocity measurements performed at CEA (Commissariat à l'Energie Atomique, France). The main and significant novelty of this paper is the use of a drag force in the momentum equations to reproduce the effects of inertial stirring instead of modelling the blades themselves. The influences of the rotational Reynolds number, the aspect ratio of the cavity, the rotating disk speed ratio and of the presence or not of impellers are investigated to get a precise knowledge of both the dynamics and the turbulence properties in the Von Karman configuration. In particular, we highlighted the transition between the merged and separated boundary layer regimes and the one between the Batchelor (1951) and the Stewartson (1953) flow structures in the smooth disk case. We determined also the transition between the one cell and the two cell regimes for both viscous and inertial stirrings

Measurement of Continuum Breakdown Using a Disc Spin-Down Experiment in Low Pressure Air

As flow becomes rarefied, a quantity called as the tangential momentum accommodation coefficient (TMAC) becomes important because it is a measure of the momentum transport from a gas molecule to a surface. Very few experimental measurements of continuum breakdown in boundary layer flows exist. All experimental measurements of the TMAC in macro-scale boundary layer flows have been done in the continuum slip and the transition flow regimes. Moreover the experimental apparatus used by previous researchers cannot accommodate for materials that are planar by nature such as those used in the field of aerospace and microfabrication. The objectives of this research include the experimental measurement of continuum breakdown in a macro-scale boundary layer flow, development of a test facility such that TMAC may be measured in the free molecular flow regime, and the measurement of TMAC for various gases versus material interactions. An experimental facility is built which consists of a disc spin down experiment in various gas pressures from atmospheric pressure through the free molecular flow regime. The real time deceleration torque is measured during the disc spin-down in each ambient pressure. The deceleration torque is non-dimensionalized suitably and is plotted against Reynolds number. The non-dimensional curves show self-similarity and therefore continuity in the viscous flow regime. Self-similarity breaks down when the viscous forces are no longer dominant and therefore it is a measure of continuum breakdown. This is also confirmed through the departure of the CFD and the semi-analytic von Karman curves from the experimental curves. A differential scavenging system is designed and incorporated into the apparatus and it facilitates measurements in the free molecular flow regime. TMAC for interactions between several gases and certain aerospace materials are measured in the free molecular flow regime. While most measurements show TMAC values of 0.7 or above in the different gases, the values are consistently low in carbon dioxide. The results are of significant impact for future space missions to Mars because the Martian atmosphere contains carbon dioxide predominantly and a lower TMAC suggests lower atmospheric drag on space vehicles

12th International Conference on Vibrations in Rotating Machinery

Since 1976, the Vibrations in Rotating Machinery conferences have successfully brought industry and academia together to advance state-of-the-art research in dynamics of rotating machinery. 12th International Conference on Vibrations in Rotating Machinery contains contributions presented at the 12th edition of the conference, from industrial and academic experts from different countries. The book discusses the challenges in rotor-dynamics, rub, whirl, instability and more. The topics addressed include: - Active, smart vibration control - Rotor balancing, dynamics, and smart rotors - Bearings and seals - Noise vibration and harshness - Active and passive damping - Applications: wind turbines, steam turbines, gas turbines, compressors - Joints and couplings - Challenging performance boundaries of rotating machines - High power density machines - Electrical machines for aerospace - Management of extreme events - Active machines - Electric supercharging - Blades and bladed assemblies (forced response, flutter, mistuning) - Fault detection and condition monitoring - Rub, whirl and instability - Torsional vibration Providing the latest research and useful guidance, 12th International Conference on Vibrations in Rotating Machinery aims at those from industry or academia that are involved in transport, power, process, medical engineering, manufacturing or construction

The 20th Aerospace Mechanisms Symposium

Numerous topics related to aerospace mechanisms were discussed. Deployable structures, electromagnetic devices, tribology, hydraulic actuators, positioning mechanisms, electric motors, communication satellite instruments, redundancy, lubricants, bearings, space stations, rotating joints, and teleoperators are among the topics covered

12th International Conference on Vibrations in Rotating Machinery

Since 1976, the Vibrations in Rotating Machinery conferences have successfully brought industry and academia together to advance state-of-the-art research in dynamics of rotating machinery. 12th International Conference on Vibrations in Rotating Machinery contains contributions presented at the 12th edition of the conference, from industrial and academic experts from different countries. The book discusses the challenges in rotor-dynamics, rub, whirl, instability and more. The topics addressed include: - Active, smart vibration control - Rotor balancing, dynamics, and smart rotors - Bearings and seals - Noise vibration and harshness - Active and passive damping - Applications: wind turbines, steam turbines, gas turbines, compressors - Joints and couplings - Challenging performance boundaries of rotating machines - High power density machines - Electrical machines for aerospace - Management of extreme events - Active machines - Electric supercharging - Blades and bladed assemblies (forced response, flutter, mistuning) - Fault detection and condition monitoring - Rub, whirl and instability - Torsional vibration Providing the latest research and useful guidance, 12th International Conference on Vibrations in Rotating Machinery aims at those from industry or academia that are involved in transport, power, process, medical engineering, manufacturing or construction

A bibliography /with abstracts/ on gas-lubricated bearings Interim report

Gas lubricated bearings - annotated bibliograph

Modeling and Simulation of Coaxial Helicopter Rotor Aerodynamics

A framework is developed for the computational fluid dynamics (CFD) analyses of a series of helicopter rotor flowfields in hover and in forward flight. The methodology is based on the unsteady solutions of the three-dimensional, compressible Navier-Stokes equations recast in a rotating frame of reference. The simulations are carried out by solving the developed mathematical model on hybrid meshes that aim to optimally exploit the benefits of both the structured and the unstructured grids around complex configurations. The computer code is prepared for parallel processing with distributed memory utilization in order to significantly reduce the computational time and the memory requirements. The developed model and the simulation methodology are validated for single-rotor-in-hover flowfields by comparing the present results with the published experimental data. The predictive merit of different turbulence models for complex helicopter aerodynamics are tested extensively. All but the κ-ω and LES results demonstrate acceptable agreement with the experimental data. It was deemed best to use the one-equation Spalart-Allmaras turbulence model for the subsequent rotor flowfield computations. First, the flowfield around a single rotor in forward flight is simulated. These time—accurate computations help to analyze an adverse effect of increasing the forward flight speed. A dissymmetry of the lift on the advancing and the retreating blades is observed for six different advance ratios. Since the coaxial rotor is proposed to mitigate the dissymmetry, it is selected as the next logical step of the present investigation. The time—accurate simulations are successfully obtained for the flowfields generated by first a hovering then a forward-flying coaxial rotor. The results for the coaxial rotor in forward flight verify the aerodynamic balance proposed by the previously published advancing blade concept. The final set of analyses aims to investigate if the gap between the two rotors of the coaxial configuration has any significant effect on the generated forces. The present results indicate either little or no such effect on the lift