H12
Biomedical 1

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13:20
conference time (CEST, Berlin)
Numerical Method to Predict the Condensation in Medical Instruments During Sterilization Process
27/10/2021 13:20 conference time (CEST, Berlin)
Room: H
A. Ansari, V. Perumal, P. Bhardwaj (Stryker Global Technology Center, IND); C. Veerappan, K.S. Ravichandran, S. Nagesh (PES University, IND)
A. Ansari, V. Perumal, P. Bhardwaj (Stryker Global Technology Center, IND); C. Veerappan, K.S. Ravichandran, S. Nagesh (PES University, IND)
Autoclaving in the medical domain is the process which uses high temperature pressurized steam to sterilize medical instruments. Ability to predict sterilization performance for a given load and autoclave operating conditions can contribute to maximizing the reliability of a complete work cycle. A Computational Fluid Dynamics methodology incorporating a suitable condensation model leading to accurate prediction of the temperature field in the autoclave chamber is a pre-requisite to be able to predict sterilization performance for a given load. Present work describes CFD modeling of the sterilization phase in an autoclave cycle using the density based wet steam model available in ANSYS FLUENT. Current approach has been arrived after a lot of efforts overcoming numerical problems (e.g. convergence, condensation capture) associated with the direct application of density based wet steam approach. Some problems w.r.t convergence and slight mass imbalance still persist. Efforts are being made to sort out such imbalance related issues. Despite these concerns simulation results show that condensation has been captured both in 2D and 3D models using the present methodology. The report describes results of steady state calculations for prescribed inlet and outlet pressure BCs for a 185L industrial scale autoclave. The chosen boundary conditions are 2.72bar and 403K at the inlet so that the chamber attains a steady state pressure of ~2bars and temperature ~395K. The outlet is a pressure boundary opening to the atmosphere. To attain quick convergence, simulation is carried out with pressure-based algorithm. Once the converged solution is achieved, the setting is then switched to density-based algorithm and subsequently wet steam model of DB algorithm is invoked on the converged solution. Thus the calculation scheme is as follows: PB-WV-SSDB-WV-SSDB-WSOFF-SS DB-WSON-SS DB-WSON-TR : where (PB:-Pressure-Based; DB:-Density-Based; WV:-Water-Vapor; SS:-Steady-State; WS:-Wet-Steam; TR:-Transient). Such step-by-step implementation of complex physics in the solver results in fairly accurate capture of steam condensation while avoiding the numerical instabilities in the entire simulation cycle.
Autoclave, Sterilization, Medical instruments, Wet steam modeling
13:40
conference time (CEST, Berlin)
Numerical Investigation of Impeller Design on the Performance of Left Ventricular Assist Device (LVAD)
27/10/2021 13:40 conference time (CEST, Berlin)
Room: H
S. Gopalakrishnan, S.S. Nair, V.V. Pillai, N.D. Sulochana (Sree Chitra Tirunal Institute for Meidcal Sciences and Technology, IND)
S. Gopalakrishnan, S.S. Nair, V.V. Pillai, N.D. Sulochana (Sree Chitra Tirunal Institute for Meidcal Sciences and Technology, IND)
Left Ventricular Assist Devices (LVAD) are rotary blood pumps which act as a continues flow circulatory support devices which assists the failing ventricle by pumping blood from left ventricle to the aorta. LVAD helps in restoring the cardiac output and mean arterial pressures to an acceptable clinically relevant levels and unloading the native ventricle. The rotating impeller inside the blood pump is critical component which is responsible for the hydraulic and hemodynamic performance of the LVAD. Rotating impeller also pose a risk of hemolysis and thrombus formation inside the blood pump which affects the performance of the device. The current Computational Fluid Dynamic (CFD) study focuses on the effect of different design features of the impeller and its interaction with pump casing on the performance of LVAD. The influence of radial vanes, offset vanes, splitter vanes and its interaction with pump volute angle and outlet angle on the performance of the pump are studied. The Computational Fluid Dynamics (CFD) studies are carried out using Ansys CFXTM. Flow is modelled as a steady, Newtonian, incompressible flow. The fluid properties like viscosity and density are considered in the study is analogous to that of blood. Moving reference frame approach, a steady state approximation of modelling rotating parts is used to model the rotation of the impeller and the turbulence is solved using Shear stress Transport k -ω (SST k-ω) Turbulence model. The pressure rise across the pump, radial velocities, flow field and wall shear stresses are compared for the different impeller vane configurations, volute and outlet angle configurations. An optimum impeller design is proposed that can meet the clinically relevant flow and pressure which also helps in unloading the native ventricle, by taking part load by the LVAD and thereby causing the recovery of the failing heart.
Left ventricular Assist Device (LVAD),CFD, Newtonian, Incompressible, Vanes, Pressure, radial velocity, wall shear stress
14:00
conference time (CEST, Berlin)
Model Based Systems Engineering in Medical Device Industry
27/10/2021 14:00 conference time (CEST, Berlin)
Room: H
S. Moda, U. Mohammad (Stryker Instruments, USA); J. Solomon, R. Rogers (gtisoft, USA)
S. Moda, U. Mohammad (Stryker Instruments, USA); J. Solomon, R. Rogers (gtisoft, USA)
Using a Multiphysics approach to create system-level models within the medical device industry could potentially decrease New Product Development (NPD) cycle times. Using system-level models would also be helpful in assisting the product teams to make optimized design choices. Optimal design decisions can be made using robust design of experiments investigations, built from knowledge of products and experimental data. In this discussion, a 0D/1D system-level model is developed using electrical, mechanical, and flow domain components to develop a system-level understanding of design performance. A model-based system engineering tool is used in this process. Component representations were built using experimental test data, and validation occurred within the tool to verify the accuracy of the representations. The system under study is divided in to electrical, fan-motor, restriction and flow split sub-systems. The electrical sub-system consists of battery and electronic board, the fan-motor system consists of a motor (linked with electrical sub-system) and a fan. The restriction subsystem represents the system restriction and the flow split sub-system represents a flow division that happens close the exhaust. All these sub-systems are modeled in 1D and are combined to form a system that can be studied at different operating conditions and configurations. Using a 1D Navier-Stokes solver, the flow system is analyzed in enough detail to make informed system-level design choices. The fan, motor, and restriction subsystems are swapped out using a design of experiments approach. The results are then analyzed to understand which components will improve system efficiency, decrease noise, and improve overall performance. This presentation will discuss the model building approach and analyze the results of the design of experiments study.
MBSE, Model bases systems engineering, 1D, Design of experiments, modeling approach, GT-Suite, Autolion, battery modeling, filtration
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