Comparisons of Rotordynamic Characteristics Predictions for Annular Gas Seals Using the Transient Computational Fluid Dynamic Method Based on Different Single-Frequency and Multifrequency Rotor Whirling Models

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Single Frequency ◽  
Solution Technique ◽  
Model Parameters ◽  
Multiple Frequency ◽  
Rotordynamic Coefficients ◽  
Gas Seals ◽  
Cfd Method

The three-dimensional (3D) transient computational fluid dynamic (CFD) method was proposed to predict rotordynamic coefficients for annular gas seals. This transient CFD method uses unsteady Reynolds-Averaged Navier–Stokes (RANS) solution technique and mesh deformation theory, which requires a rotor whirling model as the rotor excitation signal to solve the transient leakage flow field in seal and obtain the transient fluid response forces on the rotor surface. A fully partitioned pocket damper seal (FPDS) was taken as the test object to validate the present numerical method. Comparisons were made between experimental data and rotordynamic coefficient predictions using the three variations of the single-frequency and multiple-frequency rotor whirling models: (1) one-dimensional whirling model, (2) circular orbit whirling model, and (3) elliptical orbit whirling model. The numerical results show that the rotordynamic coefficients predicted by the present CFD method and six different rotor whirling models all agree well with the experiment data, and nearly coincide for all rotor whirling models. The proposed transient CFD method can be used to perform a reasonably accurate prediction of the frequency-dependent rotordynamic coefficients for annular gas seals based on any one of the present six rotor whirling models, as long as ensuring the combination of these whirling model parameters captures the small perturbation theory. The rotor whirling parameters such as whirling orbit, amplitude, and frequency number are important in predicting rotor whirling motion and fluid response forces, but have almost no effect on the computed rotordynamic coefficients. The benefit of the multiple-frequency rotor whirling models is the ability to calculate accurate rotordynamic coefficients of annular gas seals in a wide frequency range with a simulation time on the order of one-tenth the cost of the single-frequency whirling models.

A Computational Fluid Dynamics/Bulk-Flow Hybrid Method for Determining Rotordynamic Coefficients of Annular Gas Seals

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Patrick J. Migliorini ◽  
Alexandrina Untaroiu ◽  
Houston G. Wood ◽  
Paul E. Allaire
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Hybrid Method ◽  
Three Dimensional ◽  
Bulk Flow ◽  
Flow Perturbation ◽  
Rotordynamic Coefficients ◽  
Gas Seals ◽  
Cfd Method

This paper presents a new computational fluid dynamics (CFD)/bulk-flow hybrid method to determine the rotordynamic characteristics of annular gas seals. The method utilizes CFD analysis to evaluate the unperturbed base state flow, an averaging method to determine the base state bulk-flow variables, and a bulk-flow perturbation method to solve for the fluid forces acting on an eccentric, whirling rotor. In this study the hybrid method is applied to a hole-pattern seal geometry and compared with experimental data and numerical and analytical methods. The results of this study show that the dynamic coefficients predicted by the hybrid method agree well with the experimental data, producing results that are comparable with a full, three-dimensional, transient, whirling rotor CFD method. Additionally, the leakage rate predicted by the hybrid method is more agreeable with experiment than the other methods. The benefit of the present method is the ability to calculate accurate rotordynamic characteristics of annular seals that are comparable to results produced by full, transient CFD analyses with a simulation time on the order of bulk-flow analyses.

scholarly journals Orbit Decomposition Method for Rotordynamic Coefficients Identification of Annular Seals

2021 ◽  
Vol 11 (9) ◽  
pp. 4237
Author(s):  
Mingjie Zhang ◽  
Jiangang Yang ◽  
Wanfu Zhang ◽  
Qianlei Gu
Keyword(s):  
Circular Orbit ◽  
Present Method ◽  
Decomposition Method ◽  
Parameter Analysis ◽  
Elliptical Orbit ◽  
Computational Time ◽  
Solution Technique ◽  
Rotordynamic Coefficients ◽  
Cfd Method ◽  
Annular Seals

The elliptical orbit whirl model is widely used to identify the frequency-dependent rotordynamic coefficients of annular seals. The existing solution technique of an elliptical orbit whirl model is the transient computational fluid dynamics (CFD) method. Its computational time is very long. For rapid computation, this paper proposes the orbit decomposition method. The elliptical whirl orbit is decomposed into the forward and backward circular whirl orbits. Under small perturbation circumstances, the fluid-induced forces of the elliptical orbit model can be obtained by the linear superposition of the fluid-induced forces arising from the two decomposed circular orbit models. Due to that the fluid-induced forces of circular orbit, the model can be calculated with the steady CFD method, and the transient computations can be replaced with steady ones when calculating the elliptical orbit whirl model. The computational time is significantly reduced. To validate the present method, its rotordynamic results are compared with those of the transient CFD method and experimental data. Comparisons show that the present method can accurately calculate the rotordynamic coefficients. Elliptical orbit parameter analysis reveals that the present method is valid when the whirl amplitude is less than 20% of seal clearance. The effect of ellipticity on rotordynamic coefficients can be ignored.

scholarly journals DebrisInterMixing-2.3: a finite volume solver for three-dimensional debris-flow simulations with two calibration parameters – Part 2: Model validation

2017 ◽  
Author(s):  
Albrecht v. Boetticher ◽  
Jens M. Turowski ◽  
Brian W. McArdell ◽  
Dieter Rickenmann ◽  
Marcel Hürlimann ◽  
...  
Keyword(s):  
Debris Flow ◽  
Model Validation ◽  
Material Properties ◽  
Large Scale ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Clay Content ◽  
Friction Angle ◽  
Angle Of Repose ◽  
Model Parameters

Abstract. Here we present validation tests of the fluid dynamic solver presented in in v. Boetticher et al. (2016), simulating both laboratory-scale and large-scale debris-flow experiments. The new solver combines a Coulomb viscosplastic rheological model with a Herschel-Bulkley model based on material properties and rheological characteristics of the analysed debris flow. For the selected experiments in this study, all necessary material properties were known – the content of sand, clay (including its mineral composition) and gravel (including its friction angle) as well as the water content. We show that given these measured properties, two model parameters are sufficient for calibration, and a range of experiments with different material compositions can be reproduced by the model without recalibration. One calibration parameter, the Herschel–Bulkley exponent, was kept constant for all simulations. The model validation focuses on different case studies illustrating the sensitivity of debris flows to water and clay content, channel curvature, channel roughness and the angle of repose. We characterize the accuracy of the model using experimental observations of flow head positions, front velocities, run-out patterns and basal pressures.

scholarly journals DebrisInterMixing-2.3: a finite volume solver for three-dimensional debris-flow simulations with two calibration parameters – Part 1: Model description

2016 ◽  
Vol 9 (9) ◽  
pp. 2909-2923 ◽  
Author(s):  
Albrecht von Boetticher ◽  
Jens M. Turowski ◽  
Brian W. McArdell ◽  
Dieter Rickenmann ◽  
James W. Kirchner
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Clay Content ◽  
Friction Angle ◽  
Rheological Parameters ◽  
Model Description ◽  
Model Parameters ◽  
Navier Stokes Equation ◽  
Two Fluids ◽  
Rate Dependent

Abstract. Here, we present a three-dimensional fluid dynamic solver that simulates debris flows as a mixture of two fluids (a Coulomb viscoplastic model of the gravel mixed with a Herschel–Bulkley representation of the fine material suspension) in combination with an additional unmixed phase representing the air and the free surface. We link all rheological parameters to the material composition, i.e., to water content, clay content, and mineral composition, content of sand and gravel, and the gravel's friction angle; the user must specify only two free model parameters. The volume-of-fluid (VoF) approach is used to combine the mixed phase and the air phase into a single cell-averaged Navier–Stokes equation for incompressible flow, based on code adapted from standard solvers of the open-source CFD software OpenFOAM. This effectively single-phase mixture VoF method saves computational costs compared to the more sophisticated drag-force-based multiphase models. Thus, complex three-dimensional flow structures can be simulated while accounting for the pressure- and shear-rate-dependent rheology.

scholarly journals Configurable 3D Rowing Model Renders Realistic Forces on a Simulator for Indoor Training

2020 ◽  
Vol 10 (3) ◽  
pp. 734 ◽  
Author(s):  
Ekin Basalp ◽  
Patrick Bachmann ◽  
Nicolas Gerig ◽  
Georg Rauter ◽  
Peter Wolf
Keyword(s):  
Dynamic Model ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Smooth Transition ◽  
Model Parameters ◽  
Interaction Forces ◽  
New Model ◽  
Perceived Realism ◽  
Water Interaction ◽  
Resistive Forces

In rowing, rowers need outdoor and indoor training to develop a proficient technique. Although numerous indoor rowing machines have been proposed, none of the devices can realistically render the haptic, visual, and auditory characteristics of an actual rowing scenario. In our laboratory, we developed a simulator to support rowing training indoors. However, rendered forces with the initial rowing model, which was based on a simplified fluid dynamic model that approximated the drag/lift forces, were not perceived realistic enough for indoor training by expert rowers. Therefore, we implemented a new model for the blade–water interaction forces, which incorporates the three-dimensional rotation of the oar and continuously adjusts drag/lift coefficients. Ten expert rowers were asked to evaluate both models for various rowing aspects. In addition, the effect of individualization of model parameters on the perceived realism of rowing forces was elaborated. Based on the answers of the experts, we concluded that the new model rendered realistically resistive forces and ensured a smooth transition of forces within a rowing cycle. Additionally, we found that individualization of parameters significantly improved the perceived realism of the simulator. Equipped with a configurable rowing model, our simulator provides a realistic indoor training platform for rowers.

scholarly journals Numerical Investigation on Static and Rotor-Dynamic Characteristics of Convergent-Tapered and Divergent-Tapered Hole-Pattern Gas Damper Seals

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2324
Author(s):  
Dan Sun ◽  
Sheng-Yuan Li ◽  
Huan Zhao ◽  
Cheng-Wei Fei
Keyword(s):  
Dynamic Characteristics ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Rotor System ◽  
Damping Coefficient ◽  
Single Frequency ◽  
Relative Variation ◽  
Gas Damper ◽  
Rotor Dynamic ◽  
Tapered Hole

To study the influence of taper seal clearance on the static and rotor-dynamic characteristics of hole-pattern damper seals, this paper develops three-dimensional transient computational fluid dynamic methods, which comprise single-frequency and multi-frequency elliptical orbit whirl model, by the transient solution combined with a mesh deformation technique. Through the investigations, it is illustrated that: (1) In the present paper, the leakage rates of convergent-tapered hole-pattern damper seals are less than divergent-tapered hole-pattern damper seals for the same average seal clearance, and the maximum relative variation reaches 16%; (2) Compared with a constant clearance hole-pattern damper seal, the maximum relative variation of the rotor-dynamic coefficients is 1,865% for nine taper degrees in this paper; (3) Convergent-tapered hole-pattern damper seals have smaller reaction forces and effective damping coefficient, larger cross-over frequency, and direct stiffness coefficient, while divergent-tapered damper seals have the opposite effects; (4) Divergent-tapered hole-pattern damper seals alleviate the rotor whirl because of a larger effective damping coefficient when the rotor system has large natural frequency and small eccentricity. Convergent-tapered damper seals provide both sealing and journal bearing capabilities at the same time, and are more advantageous to the stability of the rotor system when rotor eccentricity is the main cause of rotor instability.

Computational Fluid Dynamic Modeling of a Mixing Stirred Reactor: Three-Dimensional Axisymmetric Models

2013 ◽  
Vol 31 (2) ◽  
pp. 147-155 ◽  
Author(s):  
Daniela Kladeková ◽  
Renáta Oriňáková ◽  
Hans-Dieter Wiemhöfer ◽  
Annamária Krajníková ◽  
Andrej Oriňák
Keyword(s):  
Dynamic Modeling ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Stirred Reactor ◽  
Computational Fluid Dynamic Modeling
Sign in / Sign up

Export Citation Format

Share Document