L6
Multiphysics 2

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10:40
conference time (CEST, Berlin)
Fluid Structure Interaction Study for the Performance Evaluation of a Newly Developed Voice Prosthesis Device
26/10/2021 10:40 conference time (CEST, Berlin)
Room: L
S. Nair, S. Sujesh, GS Akhil , K.R. Mahesh (Sree Chitra Tirunal Institute for Medical Sciences & Technology, IND); B. Varghese (Regional Cancer Centre, IND)
S. Nair, S. Sujesh, GS Akhil , K.R. Mahesh (Sree Chitra Tirunal Institute for Medical Sciences & Technology, IND); B. Varghese (Regional Cancer Centre, IND)
Total Laryngectomy that involves the complete removal of the voice box is the ultimate curative option for advanced laryngeal (voice box) cancers. The treatment however renders the patient voiceless i.e. Inability to produce any sound. A Voice Prosthesis device is used by these patients to recreate sound. This device is deployed in a puncture made through the common party wall separating the trachea (windpipe) and the oesophagus (food pipe) and the sound is generated by diverting the air from the trachea to the oesophagus through the device. The main component of the device is a one-way valve that opens under high air pressure and the recreated sound is a product of the uninterrupted flow of pulmonary air through the one-way valve and the vibrations developed in the pharyngo- oesophageal segment which acts as the “neoglottis” or the new vocal cord. A Fluid structure interaction (FSI) study was done on a new and improved version of voice prosthesis device for understanding the performance of the device. The computational model for this purpose has multiple domains, one of which is the solid domain and the other the fluid domain. The fluid domain represents the airflow path consisting of the oesophagus and trachea, and the solid domain contains the voice prosthesis device. This was done in Ansys Workbench software by using the system coupling (Fluent and Ansys structural solver) feature available in the same. Boundary conditions were applied only on the fluid domain and the deformation and the valve opening of the solid domain (device) was studied. Transient analysis was done for the study, with inlet velocity boundary condition. The velocity was provided as a function of time. The outlet had a static pressure boundary condition. A two-way system coupling was used to facilitate continuous information flow from the fluid dynamic solver to the structural solver and vice versa. Proper convergence criteria were enforced to ensure the reliability of the results. Dynamic mesh settings were used to account for the large deformation of the solid domain (valve). This setting ensured the minimum mesh quality for the continuously deforming geometries (both solid and fluid domain) by remeshing and smoothing the mesh whenever required. This study was conducted to find out the opening characteristics of the hinged valve of the voice prosthesis device.
FSI, Voice prosthesis, Total Laryngectomy
11:00
conference time (CEST, Berlin)
Multi-Physics Dynamic Modelling of an Electric Vehicle from Road to Battery
26/10/2021 11:00 conference time (CEST, Berlin)
Room: L
B. James, H. Tanner, H. Mahmoud (Romax Technology, GBR); C. Selvi (MSC Software, SWE)
B. James, H. Tanner, H. Mahmoud (Romax Technology, GBR); C. Selvi (MSC Software, SWE)
The need to engineer robust electric powertrains for passenger cars and other land vehicles is clear. The design rules that were developed for ICE-driven vehicles no longer apply, yet the market is moving too quickly for similar design rules to be developed through iterative development of electric powertrains. Simulation is the only plausible route forward. ePowertrains are highly integrated, yet the effect of this integration is hard to simulate. At the concept stage the boundary conditions for the design of each sub-system is often poorly defined or over-simplified, and even at the full-system validation/sign-off stage the interaction between the different parts of the system is poorly understood. The reason is that the full powertrain consists of many sub-systems that interact but whose physics require very heterogeneous modelling approaches. The road surface imparts shock loads that pass through the tyres, interacting via the suspension (non-linear kinematics), to the drivetrain (rotating mechanical), electric machine (electro-magnetic), inverter (electrical and control) to the battery (electro-chemical). Interactions are difficult to model with traditional “single-physics” simulation tools. This paper presents a modelling approach that combines all these domains and illustrates various phenomena by means of a representative model of an e-powertrain with realistic properties and loading conditions. The dynamic coupling that exists, not just between adjacent sub-systems but across the full powertrain, is illustrated, providing enormous insight into the behaviour of the full system. All of this is essential for successful system integration. Rather than be a high-end simulation, this approach is achieved using commonly-used simulation tools from well-known sources and can be applied by engineers with generalist skill. This accessibility delivers the democratisation of simulation needed so that the approach can be adopted widely. Furthermore, it is set up to run at an appropriate level of fidelity that produces results in a timely manner. Both of these aspects are necessary if the goals of the e-mobility revolution to be achieved.
Multi-physics, Co-simulation, Durability, E-mobility, Democratisation, System Integration
11:20
conference time (CEST, Berlin)
Overview of Electro-static Discharge (ESD) Risk Assessment in Polymer Composite Pipes used in Gas Applications
26/10/2021 11:20 conference time (CEST, Berlin)
Room: L
R. Lunn, T. London, M. Roy (TWI, GBR); A. Traidia, A. Shahran (Saudi Aramco, GBR)
R. Lunn, T. London, M. Roy (TWI, GBR); A. Traidia, A. Shahran (Saudi Aramco, GBR)
The transport of natural gas and particulates through non-metallic pipes could lead to the accumulation of static charge on the inner surface of the pipe. Due to the non-conductive nature of the pipe walls, this charge is not dissipated and may create a significant risk of explosion, damage, and injury to persons should it exceed a certain limit and discharge suddenly. Moreover, if the charge conditions across the pipe wall result in an electric field which exceeds the dielectric strength of the pipe material, then the subsequent discharge can melt a hole through the pipe wall, a phenomenon known as pin-holing. This risk has to be properly quantified and mitigated in order to ensure safe utilisation of non-metallic pipes in natural gas service. Current approaches to evaluating the risk of electrostatic discharge rely only on the determination of the flow regime (API/RP 2003 and NFPA 77), often using analytical approximations (e.g. Baker and Mandhane charts): if a mist regime is present, then the risk of electrostatic discharge is declared high. This approach can be over-conservative and mitigation methods to avoid a mist flow regime can be difficult to implement. Instead, in this work, a modelling approach combining heat transfer, computational fluid dynamics, and electrostatics has been developed to provide a quantitative assessment of the risk of electrostatic charge build-up in composite pipes used in natural gas transportation. The modelling approach consists of three levels which become progressively less conservative and the models more detailed. The modelling approach has been validated in laboratory conditions to demonstrate its efficacy and used on real case scenarios from the field. Future developments to the model will look at validating the models over a broader set of conditions and validating the impact of sand particle concentration on the electrostatic charge developed on the non-metallic pipe.
Electrostatic Discharge, Non-Metallic Pipe
11:40
conference time (CEST, Berlin)
Modelling and Numerical Analysis of Silos Under Discharge Using a Space-time Single-phase Level-set-method
26/10/2021 11:40 conference time (CEST, Berlin)
Room: L
S. Reinstädler (CENIT AG, DEU)
S. Reinstädler (CENIT AG, DEU)
A monolithic approach to fluid-structure interactions based on the space-time finite element method is presented. It is applied to investigate stress states in silos during centric and eccentric discharges. Using the continuum approach, the silo-shell is modelled as an elastic solid, whereas the bulk material is described by a model for viscoplastic compressible fluids. Between the fluid and sol-id, advanced slip boundary conditions incorporating friction are taken into account. In order to solve the governing equations of the multi-field problem, the weighted residual method is ap-plied, which is discretized by time-discontinuous space-time finite elements. Within the simulta-neous solution procedure for the coupled problem, the kinematics of both solid and fluid is de-scribed by velocities as primary variables. A mesh-moving scheme based on a pseudo-structure adapts the coordinates of the nodes in the fluid domain to the structural deformation. The non-linear system of equations composed of physical unknowns and velocities of the fluid mesh is solved iteratively applying the Newton-Raphson scheme. For the investigation of stress states inside thin-walled structures, isoparametric quadratic finite elements are applied. Whereas in structural elements uniform ansatz functions are used for both the velocities and the stresses, the fluid is discretized by quadratic Taylor-Hood elements, ap-proximating the density respectively the pressure with linear functions. The position of the free surface between bulk material and air above is given implicitly using a signed distance function, which is approximated by quadratic polynomials as well due to con-sistency. The motion of the free surface is described by the level-set-method. According to the mechanics the level-set-equation is numerically solved using a Galerkin method. Hence the mo-tion of the bulk material is not being strongly affected by the air above, a single-phase level-set-method is applied leading to meshes which in general are composed of active and inactive finite elements. Intersected elements are evaluated precisely using integration rules based on tessella-tion. A pde-based extrapolation of the velocity-field ensures an accurate transport of the free sur-face.
space-time finite elements, fluid-structure interaction, free-surface flow, single-phase level-set-method, friction model, monolithic solution, silo discharge
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