E19
Methods 1

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16:05
conference time (CEST, Berlin)
Thin Film Flow Modelling of a Vertically Rotating Disk Using an Immersed Boundary Method
28/10/2021 16:05 conference time (CEST, Berlin)
Room: E
U. Janoske, M. Bürger (Bergische Universität Wuppertal, DEU)
U. Janoske, M. Bürger (Bergische Universität Wuppertal, DEU)
Thin film flows on rotating disks can be found in various applications of chemical- and process engineering. Horizontal discs are often used for coating processes where a thin liquid layer must be distributed homogenously on the plate. Vertical discs are mainly used in plastics production for the devolatilization where thin films are advantageous to improve the transport of gaseous components. Therefore, the local distribution of the film height on the disks is essential for the determination of the required times for devolatilization. Normally, disks in industrial applications can have diameters of up to a few meters whereas film heights can be in the order of millimetres. Furthermore, the rotating discs can be perforated to provoke falling films which increase the complexity of modelling. In this study, an Immersed-Boundary Method (IBM) in combination with a Volume-of-Fluid (VoF) method to describe the two-phase flow is presented. The IBM, which is a new implementation in the open source CFD code OpenFOAM®, offers advantages to model the rotation of complex rotors compared to sliding mesh approaches. The new implementation of the Immersed Boundary Method is presented in detail showing the integration into OpenFOAM as a library and the handling of the movement of different parts which allow the modelling of real apparatuses consisting of several disks rotating with different speeds, etc. The model is validated with data from literature for a vertical rotating disk which is partially immersed in a liquid pool. The local distribution of the film height and coverage of the disk is compared to experimental data for different liquids with varying densities, viscosities and different rotational speeds of the disk. The experimental data and numerical results show a good agreement and will be discussed for the different cases of the experiment. A perspective on further applications of the IBM is given as well.
Film flow, Volume-of-Fluid, Immersed Boundary Method, CFD, rotating disk
16:25
conference time (CEST, Berlin)
Calculation of Pump Characteristics with Operating Point-Adapted Computational Meshes
28/10/2021 16:25 conference time (CEST, Berlin)
Room: E
P. Galpin (ISimQ Ltd, CAN); G. Scheuerer, T. Hansen (ISimQ GmbH, DEU); N. Wyman (Pointwise Inc., USA)
P. Galpin (ISimQ Ltd, CAN); G. Scheuerer, T. Hansen (ISimQ GmbH, DEU); N. Wyman (Pointwise Inc., USA)
A new mesh adaptation procedure is developed that is well suited to challenging turbomachinery CFD simulations. The adaptation procedure creates a mesh that robustly conforms to the underlying geometry, that respects user-defined locally anisotropic boundary layer mesh refinement for efficiency, and that is driven by an adaptation sensor that accurately resolves large as well as subtle secondary flow features. The method seeks to control numerical error in the discrete solution by minimizing the truncation error based on the CFD solver discretization. An adaptation sensor is developed for a node-centred finite volume CFD solver, including control over the rate at which the mesh size increases with each adaptation step. The adaptation sensor is used to define a target size field for an updated discrete mesh conforming to the underlying CAD geometry. The mesh adaptation procedure is demonstrated across the speedline of a pump for flow ranging from 80% to 120% of the design flow rate. Both the pump impeller and volute are modeled, using a steady-state frame change interface between the rotating and stationary components. Operating point independent adaptation is performed, creating adapted meshes unique to the local flow conditions and features for each operating condition. Adaptation is performed at each operating point until a target average discretisation truncation error is achieved, ensuring that the numerical error is consistently reduced for all operating points across the speedline. In addition to the truncation error, the impeller head, power and volute losses are evaluated across the speedline, as a function of the mesh adaptation cycle. It is seen that off-design operating points require more mesh adaptation relative to the design point flow. Computational effort of the adaptation procedure is summarised and compared to the effort that would be required to achieve a similar level of truncation error by a manual mesh refinement approach.
CFD, adaptation, turbomachinery, pump, numerics
16:45
conference time (CEST, Berlin)
Virtual Blade Model Utilising Artificial Intelligence Driven 3D Corrections
28/10/2021 16:45 conference time (CEST, Berlin)
Room: E
G. Zipszer, B. Darázs, M. Gyöngyösi, Á. Horváth (eCon Engineering Kft., HUN)
G. Zipszer, B. Darázs, M. Gyöngyösi, Á. Horváth (eCon Engineering Kft., HUN)
At eCon Engineering Kft. a conventional Virtual Blade Model (VBM) linked with blade element theory was developed and implemented in a commercial Computational Fluid Dynamics software of finite volume approach (ANSYS Fluent). The integration of the Virtual Blade Model (VBM) was achieved via User Defined Functions (UDF) written in C programming language which carries out the calculation of the spanwise load distribution along the propeller blade using available 2D profile data, such as lift and drag coefficients. Our VBM model accounts for not only the radial but the azimuthal variation of the propeller inflow and calculates the additional momentum source terms accordingly. This model was further enhanced by applying 3D aerodynamic corrections derived by Artificial Intelligence (AI) algorithm improving the VBM spanwise load distribution prediction capability leading to a better approximation of 3D flow field which would be induced by the propeller. The changes in downstream turbulence level is also calculated with the help of the AI algorithm. The AI model was trained using isolated explicit 3D propeller blade simulations. There is an increasing need for the capability to accounting for the effects of propeller induced flow on the airframe during small and medium size aircraft design. Being aware of the propeller induced flow field from the beginning of the design process could save significant time and cost later in the optimisation and prototyping stages. Also, it can ensure improved product performance which is sought for by many aircraft developers. Using Computational Fluid Dynamics (CFD) models explicitly including the propeller blades comes with high costs, therefore it is unaffordable during the initial stages of product development. Our Virtual Blade Model (VBM) applying Artificial Intelligence (AI) to derive 3D corrections and turbulence intensity predictions can be used as a cost-effective alternative, but with improved performance compared to conventional Virtual Blade Models.
virtual blade model, VBM, artificial intelligence, AI, 3D corrections
17:05
conference time (CEST, Berlin)
Application of Spectral Element Method for Solving Problems With a Cyclic Symmetry at Unstructured Non-conformal Curvilinear Meshes
28/10/2021 17:05 conference time (CEST, Berlin)
Room: E
A. Vershinin, V. Levin (Lomonosov Moscow State University, RUS); A. Kukushkin, D. Konovalov (Fidesys LLC, RUS)
A. Vershinin, V. Levin (Lomonosov Moscow State University, RUS); A. Kukushkin, D. Konovalov (Fidesys LLC, RUS)
An approach for the numerical simulation of cyclic symmetry conditions on non-conformal curvilinear meshes using spectral element method is presented. The multi point constraints (MPC) method [1,2] is used to set the imposed displacement constraints and the Direct elimination method in matrix form is used to add them to the system of equations with mass and stiffness matrices. When forming MPC conditions on non-conformal meshes, it is proposed to rotate the surfaces on which the conditions of cyclic symmetry are set, and then search for the projection of the master-node onto the slave-surface by the method used in the search for contact pairs [4]. Further, the constraint equations are combined together for the original (not rotated) node and its projection. The conditions of equality of displacements and equality of normal stresses are imposed at cyclic surfaces. An algorithm for transforming constraints to identify the principal and dependent degrees of freedom is described. A direct elimination method is proposed to exclude the dependent degrees of freedom from the finite element system of linear equations. The influence of a symmetrization matrix additional to the stiffness matrix and containing the condition of equality of normal stresses is considered. Algorithm was implemented in CAE FIDESYS [5]. As an example of application of the developed algorithm, solutions of several problems with cyclic symmetry are considered. The proposed approach makes it possible to specify conditions of cyclic symmetry, which are fulfilled exactly, in contrast to penalty methods. And at the same time, the developed algorithm allows the use of non-conformal curvilinear grids, which simplifies a mesh generation process and provides high accuracy in the discretization of complex geometric CAD-models. The reported study was funded by Russian Science Foundation project - 19-77-10062. References: [1] Abel J and Shephard M 1979 An algorithm for multipoint constraints in finite element analysis Int. J. Numer. Meth. Engng 14 pp 464–467 [2] Felippa C 2004 Introduction to finite element methods. Chapter 8 Multifreedom constraints I. Colorado, Department of Aerospace Engineering Sciences and Center for Aerospace Structures University of Colorado Boulder pp 1-17 [3] Kukushkin A, Konovalov D, Vershinin A and Levin V Numerical simulation in CAE Fidesys of bonded contact problems on non-conformal meshes 2019 J. Phys.: Conf. Ser. 1158 032022 [4] Zienkiewicz O and Taylor R 2014 The Finite Element Method for Solid and Structural Mechanics Seventh Edition (Amsterdam: Elsevier) [5] www.cae-fidesys.com
Cyclic symmetry, Spectral Element Method, SEM, multi point constraints ,MPC
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