The Experts below are selected from a list of 29253 Experts worldwide ranked by ideXlab platform

Jaw-ren Lin - One of the best experts on this subject based on the ideXlab platform.

  • Purely squeezing film characteristics in partial porous journal bearings with infinite length
    Industrial Lubrication and Tribology, 2004
    Co-Authors: Chi-ren Hung, Long-jin Liang, Tong‐bou Chang, Jaw-ren Lin
    Abstract:

    The influences of Viscous Shear stresses on the squeezing film behaviors in porous journal bearings with infinite length are analyzed. Based on the Brinkman model, two general coupled Reynolds‐type equations derived between two curved surfaces are applied to evaluate the bearing characteristics. According to the results obtained, the Brinkman model predicts quite different squeezing film performances to those obtained by using the slip‐flow model and the Darcy model. In addition, the quantitative effects of Viscous Shear stresses of the Brinkman model upon the porous squeezing film characteristics are more pronounced for porous journal bearings with moderate permeability parameters and higher eccentricity ratios.

  • Viscous Shear effects on the squeeze-film behavior in porous circular disks
    International Journal of Mechanical Sciences, 1996
    Co-Authors: Jaw-ren Lin
    Abstract:

    On the basis of the Brinkman model (BM), the main objective of this paper is to predict the Viscous Shear effects on the squeeze-film characteristics between porous circular disks. According to the results obtained, the influences of Viscous Shear stresses on the squeeze-film behavior are significant and not negligible. It is found that the BM predicts quite different squeeze-film action to those derived by using the Slip-flow model (SFM) and Darcy model (DM). When comparing with that of the SFM, the Viscous Shear effects of the BM provide an enhancement in the load-carrying capacity and, then, increase the response time of the squeeze-film behavior; but these trends are reversed as compared to that derived by using the DM.

  • Squeeze film behavior in a hemispherical porous bearing using the Brinkman model
    Tribology Transactions, 1996
    Co-Authors: Jaw-ren Lin
    Abstract:

    On the basis of the Brinkman model, the main objective of this paper is to theoretically predict the effects of Viscous Shear stresses on the pure squeeze film behavior in a hemispherical porous bearing under a constant load. The modified Reynolds equation is derived by using the Brinkman equations to account for the Viscous Shear effects. According to the results, the influence of Viscous Shear stresses on the squeeze film characteristics is significant and not negligible. It is also found that the Brinkman model predicts a quite different squeeze film action than those derived by the Darcy model and the slip-flow model. Compared with that derived by the Darcy model for thin-walled porous bearings, the Viscous Shear effects of the Brinkman model reduce the load capacity and the response time of the squeeze film, but the Viscous Shear effects increase the load capacity and lengthen the response lime of the squeeze film action for rotor-bearing contact to occur as compared to that of the slip-flow model. M...

  • Hydrodynamic lubrication of long, flexible, porous journal bearings using the Brinkman model
    Wear, 1996
    Co-Authors: Jaw-ren Lin, Chi Chuan Hwang, Rong Fuh Yang
    Abstract:

    Considering the flexibility of porous bearings, this paper applies the Brinkman model (BM) to study the influences of Viscous Shear stresses on the lubrication performance of long, flexible, porous journal bearings. It is found that the Viscous Shear effects of the BM signify an improvement in the steady characteristics of the system. A comparison with the Darcy model (DM) shows that the Viscous Shear effects provide a significant reduction in the eccentricity ratio and ensure a noticeable reduction in the friction parameter at high loads.

  • Lubrication of Long Porous Slider Bearings : Use of the Brinkman-Extended Darcy Model
    JSME International Journal Series B, 1996
    Co-Authors: Chi Chuan Hwang, Jaw-ren Lin, Rong Fuh Yang
    Abstract:

    We apply the Brinkman-extended Darcy model to analyze the hydrodynamic lubrication of long porous slider bearings. The solutions are obtained and compared with those based on the Darcy model. The results show that the effects of Viscous Shear given by the Brinkman-extended Darcy model lead to a higher load capacity and a lower friction parameter. It is found that a thicker porous bearing gives a greater effect of Viscous Shear on load capacity and friction parameter.

Ingo R. Titze - One of the best experts on this subject based on the ideXlab platform.

  • Hyaluronic acid (with fibronectin) as a bioimplant for the vocal fold mucosa.
    The Laryngoscope, 1999
    Co-Authors: Roger W. Chan, Ingo R. Titze
    Abstract:

    Objectives To measure the viscoelastic Shear properties of hyaluronic acid, with and without fibronectin, and to compare them with those of the human vocal fold mucosa and other phonosurgical biomaterials. Methods Viscoelastic Shear properties of various implantable biomaterials (Teflon, gelatin, collagen, fat, hyaluronic acid, and hyaluronic acid with fibronectin) were measured with a parallel-plate rotational rheometer. Elastic and Viscous Shear properties were quantified as a function of oscillation frequency (0.01-15 Hz) at 37 degrees C. Results The Shear properties of hyaluronic acid were relatively close to those of human vocal fold mucosal tissues reported previously. Hyaluronic acid at specific concentrations (0.5%-1%), with or without fibronectin, was found to exhibit Viscous Shear properties (Viscous Shear modulus and dynamic viscosity) similar to those of the average male and female vocal fold mucosa. Conclusions According to a theory that establishes the effects of tissue Shear properties on vocal fold oscillation, phonation threshold pressure (a measure of the ease of phonation) is directly related to the Viscous Shear modulus of the vibrating vocal fold mucosa. Therefore, our findings suggest that hyaluronic acid, either by itself or mixed with fibronectin, may be a potentially optimal bioimplant for the surgical management of vocal fold mucosal defects and lamina propria deficiencies (e.g., scarring) from a biomechanical standpoint.

  • Hyaluronic acid (with fibronectin) as a bioimplant for the vocal fold mucosa.
    The Laryngoscope, 1999
    Co-Authors: Roger W. Chan, Ingo R. Titze
    Abstract:

    To measure the viscoelastic Shear properties of hyaluronic acid, with and without fibronectin, and to compare them with those of the human vocal fold mucosa and other phonosurgical biomaterials. Viscoelastic Shear properties of various implantable biomaterials (Teflon, gelatin, collagen, fat, hyaluronic acid, and hyaluronic acid with fibronectin) were measured with a parallel-plate rotational rheometer. Elastic and Viscous Shear properties were quantified as a function of oscillation frequency (0.01-15 Hz) at 37 degrees C. The Shear properties of hyaluronic acid were relatively close to those of human vocal fold mucosal tissues reported previously. Hyaluronic acid at specific concentrations (0.5%-1%), with or without fibronectin, was found to exhibit Viscous Shear properties (Viscous Shear modulus and dynamic viscosity) similar to those of the average male and female vocal fold mucosa. According to a theory that establishes the effects of tissue Shear properties on vocal fold oscillation, phonation threshold pressure (a measure of the ease of phonation) is directly related to the Viscous Shear modulus of the vibrating vocal fold mucosa. Therefore, our findings suggest that hyaluronic acid, either by itself or mixed with fibronectin, may be a potentially optimal bioimplant for the surgical management of vocal fold mucosal defects and lamina propria deficiencies (e.g., scarring) from a biomechanical standpoint.

Roger W. Chan - One of the best experts on this subject based on the ideXlab platform.

  • Hyaluronic acid (with fibronectin) as a bioimplant for the vocal fold mucosa.
    The Laryngoscope, 1999
    Co-Authors: Roger W. Chan, Ingo R. Titze
    Abstract:

    Objectives To measure the viscoelastic Shear properties of hyaluronic acid, with and without fibronectin, and to compare them with those of the human vocal fold mucosa and other phonosurgical biomaterials. Methods Viscoelastic Shear properties of various implantable biomaterials (Teflon, gelatin, collagen, fat, hyaluronic acid, and hyaluronic acid with fibronectin) were measured with a parallel-plate rotational rheometer. Elastic and Viscous Shear properties were quantified as a function of oscillation frequency (0.01-15 Hz) at 37 degrees C. Results The Shear properties of hyaluronic acid were relatively close to those of human vocal fold mucosal tissues reported previously. Hyaluronic acid at specific concentrations (0.5%-1%), with or without fibronectin, was found to exhibit Viscous Shear properties (Viscous Shear modulus and dynamic viscosity) similar to those of the average male and female vocal fold mucosa. Conclusions According to a theory that establishes the effects of tissue Shear properties on vocal fold oscillation, phonation threshold pressure (a measure of the ease of phonation) is directly related to the Viscous Shear modulus of the vibrating vocal fold mucosa. Therefore, our findings suggest that hyaluronic acid, either by itself or mixed with fibronectin, may be a potentially optimal bioimplant for the surgical management of vocal fold mucosal defects and lamina propria deficiencies (e.g., scarring) from a biomechanical standpoint.

  • Hyaluronic acid (with fibronectin) as a bioimplant for the vocal fold mucosa.
    The Laryngoscope, 1999
    Co-Authors: Roger W. Chan, Ingo R. Titze
    Abstract:

    To measure the viscoelastic Shear properties of hyaluronic acid, with and without fibronectin, and to compare them with those of the human vocal fold mucosa and other phonosurgical biomaterials. Viscoelastic Shear properties of various implantable biomaterials (Teflon, gelatin, collagen, fat, hyaluronic acid, and hyaluronic acid with fibronectin) were measured with a parallel-plate rotational rheometer. Elastic and Viscous Shear properties were quantified as a function of oscillation frequency (0.01-15 Hz) at 37 degrees C. The Shear properties of hyaluronic acid were relatively close to those of human vocal fold mucosal tissues reported previously. Hyaluronic acid at specific concentrations (0.5%-1%), with or without fibronectin, was found to exhibit Viscous Shear properties (Viscous Shear modulus and dynamic viscosity) similar to those of the average male and female vocal fold mucosa. According to a theory that establishes the effects of tissue Shear properties on vocal fold oscillation, phonation threshold pressure (a measure of the ease of phonation) is directly related to the Viscous Shear modulus of the vibrating vocal fold mucosa. Therefore, our findings suggest that hyaluronic acid, either by itself or mixed with fibronectin, may be a potentially optimal bioimplant for the surgical management of vocal fold mucosal defects and lamina propria deficiencies (e.g., scarring) from a biomechanical standpoint.

T Gao - One of the best experts on this subject based on the ideXlab platform.

  • deformation of elastic particles in Viscous Shear flow
    Journal of Computational Physics, 2009
    Co-Authors: T Gao
    Abstract:

    In this paper, the dynamics of two dimensional elastic particles in a Newtonian Viscous Shear flow is studied numerically. To describe the elastic deformation, an evolution equation for the Eulerian Almansi strain tensor is derived. A constitutive equation is thus constructed for an incompressible ''Neo-Hookean'' elastic solid where the extra stress tensor is assumed to be linearly proportional to the Almansi strain tensor. The displacement field does not appear in this formulation. A monolithic finite element solver which uses Arbitrary Lagrangian-Eulerian moving mesh technique is then implemented to solve the velocity, pressure and stress in both fluid and solid phase simultaneously. It is found that the deformation of the particle in the Shear flow is governed by two non-dimensional parameters: Reynolds number (Re) and Capillary number (Ca, which is defined as the ratio of the Viscous force to the elastic force). In the Stokes flow regime and when Ca is small (Ca<0.65), the particle deforms into an elliptic shape while the material points inside the particle experience a tank-treading like motion with a steady velocity field. The deformation of the elastic particle is observed to vary linearly with Ca, which agrees with theoretical results from a perturbation analysis. Interactions between two particles in a Viscous Shear flow are also explored. It is observed that after the initial complicated interactions, both particles reach an equilibrium elliptic shape which is consistent with that of a single particle.

  • Deformation of elastic particles in Viscous Shear flow
    Journal of Computational Physics, 2009
    Co-Authors: T Gao
    Abstract:

    In this paper, the dynamics of two dimensional elastic particles in a Newtonian Viscous Shear flow is studied numerically. To describe the elastic deformation, an evolution equation for the Eulerian Almansi strain tensor is derived. A constitutive equation is thus constructed for an incompressible ''Neo-Hookean'' elastic solid where the extra stress tensor is assumed to be linearly proportional to the Almansi strain tensor. The displacement field does not appear in this formulation. A monolithic finite element solver which uses Arbitrary Lagrangian-Eulerian moving mesh technique is then implemented to solve the velocity, pressure and stress in both fluid and solid phase simultaneously. It is found that the deformation of the particle in the Shear flow is governed by two non-dimensional parameters: Reynolds number (Re) and Capillary number (Ca, which is defined as the ratio of the Viscous force to the elastic force). In the Stokes flow regime and when Ca is small (Ca

A. Baïri - One of the best experts on this subject based on the ideXlab platform.

  • free convection in parallelogram shaped enclosures with isothermal active walls Viscous Shear stress in active systems
    Fluid Dynamics Research, 2012
    Co-Authors: A. Baïri, E Zarcopernia, Jm Garcia De Maria, Najib Laraqi
    Abstract:

    Thermocouples are often used for thermoregulation of active thermal systems. When the junctions of these sensors are under a natural convection flow, it is necessary to take into account the Viscous stress that can affect the measurement of temperature and therefore the regulation set points. The main objective of this work is to study the Viscous Shear stress taking place close to the active hot wall in closed air-filled cavities of parallelogrammic shape. The influence of Shear stress is examined for different inclination angles of the cavity and large Rayleigh numbers which are usual in thermal applications. The local stress distributions are presented for the steady state for all the geometric configurations considered. The Nusselt number at the hot wall as well as the temperature and stream function distributions in the cavities are also included. The findings obtained from the numerical simulation using the finite volume method are validated by thermal measurements on an experimental cavity. This study confirms the need to properly choose the location of thermocouples in the reference cell used for controlling the active system.

  • effects of Viscous Shear stress on thermoregulation of electronics transient free convection in diode enclosures induced by discrete heat bands under constant heat flux
    Applied Thermal Engineering, 2011
    Co-Authors: A. Baïri
    Abstract:

    Abstract Thermal and dynamic phenomena that occur in the immediate vicinity of electronic components during operation generate Viscous Shear stresses due to velocity gradients. When thermocouples used for thermal regulation of these assemblies are installed in this environment, temperature measurements may be erroneous. It is therefore essential to take into account Viscous effects in the boundary layer when dealing with thermal control of electronics subjected to natural convection. These phenomena are particularly pronounced and complex when generation of heat at the active wall is not uniform. That is the case for the real device treated in this work. The natural convective flow is generated by a vertical wall composed by alternated adiabatic and heated bands under constant heat flux, representing a working electronic equipment. The 2D transient boundary layer near the vertical active hot wall of parallelogram-shaped enclosures is treated in order to determine the Viscous Shear stress. Results are obtained by numerical approach using the finite volume method and some measurements. Many geometrical configurations are treated while varying the inclination angle of the top and bottom passive adiabatic walls. The very different local distributions of Viscous Shear stresses and vertical thermal gradients confirm the necessity to take them into account to properly install the sensors used for thermoregulation.

  • Effects of Viscous Shear stress on thermoregulation of electronics. Transient free convection in diode enclosures induced by discrete heat bands under constant heat flux
    Applied Thermal Engineering, 2011
    Co-Authors: A. Baïri
    Abstract:

    Thermal and dynamic phenomena that occur in the immediate vicinity of electronic components during operation generate Viscous Shear stresses due to velocity gradients. When thermocouples used for thermal regulation of these assemblies are installed in this environment, temperature measurements may be erroneous. It is therefore essential to take into account Viscous effects in the boundary layer when dealing with thermal control of electronics subjected to natural convection. These phenomena are particularly pronounced and complex when generation of heat at the active wall is not uniform. That is the case for the real device treated in this work. The natural convective flow is generated by a vertical wall composed by alternated adiabatic and heated bands under constant heat flux, representing a working electronic equipment. The 2D transient boundary layer near the vertical active hot wall of parallelogram-shaped enclosures is treated in order to determine the Viscous Shear stress. Results are obtained by numerical approach using the finite volume method. Many geometrical configurations are treated while varying the inclination angle of the top and bottom passive adiabatic walls. The very different local distributions of Viscous Shear stresses and vertical thermal gradients confirm the necessity to take them into account to properly install the sensors used for thermoregulation.

  • thermoregulation of electronics inside diode enclosures Viscous Shear stress in 2d natural convection generated by isothermal active walls
    International Conference on Communications, 2011
    Co-Authors: A. Baïri, E Zarcopernia, Najib Laraqi, I Bairi, J Garcia M De Maria, Bravo A Malo
    Abstract:

    Correct operation of electronic assemblies is subject to their regulation in the temperature range recommended by manufacturers. It is therefore necessary to control the heat exchange phenomena that affect them. When thermoregulation of these assemblies is based on thermocouples, the effects of fluid flow on the junctions of these sensors must be considered, particularly the thermal and velocity gradients. This prevents measurement errors that can be detrimental to the proper functioning of the equipment. The main objective of this study concerns the examination of the Viscous stresses that occur by natural convection in parallelogram-shaped cavities containing electronic equipments. These enclosures, called diode cavities in the convective heat transfer sense, lead to very different flows depending on the geometry. Many geometrical configurations are treated while varying the inclination angle of the top and bottom passive adiabatic walls. A detailed study of the boundary layer is used to find the distribution of Viscous Shear stresses and the heat exchanged by natural convection through the Nusselt number. The numerical approach is made using the finite volume method. The results are confirmed by previous numerical and experimental works, and allow to better control thermoregulation of electronic assemblies by means of thermocouples.