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Many industries rely on heavy-duty machinery such as cranes, pipelines, motors, which are subject to wear and tear. Milling of such parts using conventional machine tools presents many drawbacks and is impossible in some cases. In such situations, mobile machine tools can be used to machine directly on site. However, mobile machines are flexible, and are prone to detrimental vibrations during cutting operations. Vibrational stability in the surfacing process has been extensively studied in conventional milling. However, the focus of this article is an original study on a mobile milling machine used for on-site surfacing operations. An experimental investigation into the vibrational behavior of the machine is carried out and a sensorless method is used to detect the onset of chatter. Machine flexibility is discussed using a tool-point frequency response function and references from the literature. Milling operations are carried out over a range machining parameter to determine an experimental stability limit. Internal sensors for spindle motor consumption and spindle motor encoder are monitored during the machining process. A threshold is established for determining the appearance of chatter using only the machine’s internal sensors.

This paper deals with an experimental, theoretical and numerical study of a turbulent flow with separated boundary layers between a rotor and a stator. The system is not subjected to any superimposed radial flow. The periphery of the cavity is opened to the atmosphere so that the solid body rotation for infinite discs is not always observed. Emphasis was placed on development of an asymptotic approach and a step-by-step method to compute the radial distribution of the core swirl ratio and the static pressure on the stator side. The theory also includes the radial and axial velocities in the core region. The numerical simulation has been conducted with the commercial CFD code Fluent 6.1. The k-ωSST turbulence model is used, with the assumption of 2D-axisymmetric and steady flow. CFD validations have been performed by comparison of the numerical results with the corresponding theoretical results. Numerical and experimental results are in good agreement with analytical solutions.

The present study is devoted to the influence of a superposed radial inflow in a rotor-stator cavity with a peripheral opening. The flow regime is turbulent, the two boundary layers being separated by a core region. An original theoretical solution is obtained for the core region, explaining the reason why a weak radial inflow has no major influence near the periphery of the cavity but strongly affects the flow behavior near the axis. The validity of the theory is tested with the help of a new set of experimental data including the radial and tangential mean velocity components, as well as three components of the Reynolds stress tensor measured by hot-wire anemometry. The theoretical results are also in good agreement with numerical results obtained with the Fluent code and experimental data from the literature.

The applications of high performance materials in the aerospace and in the automotive technology in the next years need to develop new vibration study, nondestructive testing, predictive maintenance and industrial control methods.The Laser Scanning Vibrometry and Holographic Interferometry methods of vibration study and nondestructive testing by modal analysis are described. The Laser Scanning Vibrometer PSV 400 is made by Polytec GmbH and the PSV software reconstructs the 3D model of the measured micro-deformation of the object. The holographic laser system HLS-3 from Lumonics Inc. has 100 MW ruby laser peak power and 30 ns pulse width.Using mechanical excitation to induce a measurable vibration, the Laser Scanning Vibrometry and Holographic Interferometry modal analysis measurements show up the vibrational signatures and the damaged areas of the objects made by high performance materials - polymers, composites.

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.

Resume Des experiences consacrees a l'etude des effets produits par un changement de geometrie peripherique dans un systeme rotor-stator ont permis de mettre en evidence une extreme sensibilite a l'egard d'une faible variation du rapport des rayons des deux disques, entrainant le passage brutal d'un regime d'ecoulement a un autre. A nombre de Reynolds et distorsion donnes, l'ecoulement tend vers la solution correspondant a des disques de rayons infinis uniquement lorsque le rapport du rayon du stator a celui du rotor est suffisamment grand.

The present work examines the turbulent flow in a rotor-stator system subjected to a radial inflow and heat transfer effects. In the scope of this study, compressibility can be neglected which leads us to dissociate the heat transfer process from the dynamical effects. A method for making simultaneous temperature and velocity measurements is used to provide qualitative and quantitative data. An analysis of the results and comparisons with a theoretical prediction issued from an asymptotical formulation brings typical properties of the flow to light.

The present study is devoted to the influence of a superposed centripetal flow q in a rotor-stator cavity with a peripheral opening. In the literature, previous works have already shown that a weak radial inflow has no major influence near the periphery of the cavity, whereas the flow behavior is strongly modified when approaching the axis [1–2]. The challenge of this work is to give a better understanding of this phenomenon. Attention is focused on a rotor-stator system characterized by a small gap ratio G and high Reynolds number Re, so that the flow is divided into two boundary layers separated by a core region, according to the classification by Daily and Nece [3]. Until now, numerous authors obtained analytical solutions for the central core flow behavior: following the analysis performed by Schlichting [4], and assuming that the evolution of the velocity in the Ekman boundary layer corresponds to a 1/7 power law, Poncet et al. [2] proposed an analytical law predicting the evolution of the core swirl ratio K versus a local dimensionless coefficient of flow rate Cqr . Debuchy et al. [5] improved this last solution by taking into account the radial exchange of fluid outside the boundary layers. This last approach was used by Abdel Nour et al. [6] in a rotor-stator cavity without any superposed flow (isolated cavity). They obtained an original analytical law, different from the classical similitary solution proposed by Batchelor [7] in the case of infinite disc, convenient for a cavity with peripheral opening and small pre-swirl ratio. In this paper, the authors present an original analytical law in order to model the central core flow behavior in a rotor-stator cavity subjected to a very weak inflow rate (q → 0). The validity of the solution is tested with the help of: • a new set of experimental data including the radial and tangential mean velocity measured by hot-wire anemometry, • experimental results from the literature.Copyright © 2011 by ASME

International audience; Author(s): Roger Debuchy IUT de Béthune, Laboratoire de Mécanique de Lille UMR 8107, PRES Université Nord de France, 1230 Rue de l'université BP 819, 62408 Béthune Cedex, France Fadi Abdel Nour and Gérard Bois Arts et Métiers ParisTech, Laboratoire de Mécanique de Lille UMR 8107, PRES Université Nord de France, 8, Boulevard Louis XIV, 59046 Lille Cedex, France In the most part of an enclosed rotor-stator system with separated boundary layers, the flow structure is characterized by a central core rotating as a solid body with a constant core-swirl ratio. This behavior is not always observed in an isolated rotor-stator cavity, i.e., without any centripetal or centrifugal throughflow, opened to the atmosphere at the periphery: Recent works have brought to evidence an increasing level of the core-swirl ratio from the periphery to the axis, as in the case of a rotor-stator with superposed centripetal flow. The present work is based on an asymptotical approach in order to provide a better understanding of this process. Assuming that the boundary layers behave as on a single rotating disk in a stationary fluid on the rotor side, and on a stationary disk in a rotating fluid on the stator side, new analytical relations are obtained for the core-swirl ratio, the static pressure on the stator, and also the total pressure at midheight of the cavity. An experimental study is performed: Detailed measurements provide data for several values of the significant dimensionless parameters: 1.14

This work relates to an experimental, theoretical and numerical study of a turbulent flow with separated boundary layers between a rotating disc (rotor) and a stationary one (stator) without any superposed radial flow. The originality of this study is that the pre-swirl ratio at the periphery of the cavity (Kp ) is lower than the core swirl ratio (KB ) corresponding to the solid body rotation, as predicted by Batchelor in the case of infinite discs: this is what the authors call a rotor-stator system with low pre-swirl ratio. Under these conditions, recent works have shown that the core swirl ratio (K) is a decreasing function of the radius, at least in the peripheral region. This behaviour has rather been observed in the cavities with superposed centripetal radial flow. In the present paper, this flow property is explained starting from an asymptotic approach which leads to step-by-step analytical computation method of the radial distribution of the core swirl ratio (K) and of the static pressure on the stator side p*. The validation of the theory is based both on experimental and numerical results. The experimental tests are carried out in a rotor-stator cavity for different values of the pre-swirl ratio, which is done by geometrical changes of the periphery of the system. The experimental data mostly include the velocity measurements and the turbulent correlations by hot-wire anemometry in interstice between the discs, as well as the static pressure measurements on the stator side. Comparisons with predictions from the CFD code Fluent are also provided. The numerical simulations are performed using the two-equation k – ω SST turbulence model, assuming a 2D-axisymmetric steady flow, in a domain corresponding to the inter-disks spacing and the peripheral outer region of the cavity. Computed and experimental values are in good agreement with the theoretical results.Copyright © 2009 by ASME

International audience; The present work considers the turbulent air flow inside an annular high speed rotor-stator cavity opened to the atmosphere at the periphery, where the pre-swirl ratio of the fluid is low. The interdisk spacing is sufficiently large so that the boundary layers developed on each disk are separated and the flow belongs to the regime IV of Daily and Nece (ASME J. Basic Eng. 82 (1960) 217–232). In such a system, the solid body rotation of the core predicted by Batchelor (J. Mech. Appl. Math. 4 (1951) 29–41) in case of infinite disks is not always observed: the flow behaviour in the whole interdisk spacing is governed by the level of the pre-swirl velocity of the fluid which is closely linked to the peripheral geometry (Debuchy et al., Int. J. Rotating Machinery, (2007)). In the first part of the paper, experimental results performed by hot-wire probes introduced through the stator including mean radial and tangential velocity components, as well as three turbulent correlations, are presented for several peripheral boundary conditions leading to the same value of the pre-swirl ratio. In the second part, comparisons between experiments, numerical and analytical results are provided. The numerical approach is based on the Reynolds Stress Modeling (RSM) developed by Elena and Schiestel (Int. J. Heat Fluid Flow 17 (1996) 283–289). A good agreement between the different approaches is obtained for the mean and turbulent fields and especially for the distribution of the core swirl ratio.