## Selected Publications:

### – Onset of levitation in thrust bearing: FSI study using Abaqus-FlowVision coupling

Collaboration with:

Taiwan Power Company

Abstract: Lift force formation in a thrust bearing of 800-tons rotor of electric power station is discussed in the given paper. The problem is solved numerically. Direct coupling between finite element system Abaqus calculating stress and strain state of an bearing parts and finite-volume system FlowVision-HPC calculating oil flow in gap between a collar and a shoe of bearing is used. The shape of the gap between the shoe and the collar, the clearance value, the moment of the friction force, and the temperature distribution of oil over the clearance are determined.

### – Simulating the Pouch Forming Process Using a Detailed Fluid-Structure Interaction

Collaboration with:

TetraPak

Abstract: A deeper understanding of the interaction between machine, packaging material and liquid product during the forming process of pouches is enabled by the use of numerical simulation.Tetra Pak pouch forming system forms the pouches in a continuous fashion starting from a tube of packaging material filled with the liquid to be packaged.A bunch of jaws, moved with special laws, shape the tube of packaging material into pouches. The liquid into the tube is supplied through an inlet pipe, placed inside the tube. Additionally a pouch forming systems has a counter-pressure flange and a floater that moves along the inlet pipe and floats on top of the liquid column. The floater is used to control the flow rate at the inlet pipe.Thus a complex problem with flexible walls, free surface flows and kinematic motion of different bodies under hydrodynamic and gravity forces needs to be simulated.Simulating the pouch forming, including a detailed fluid-structure interaction is the goal of this paper. The simulation is performed coupling Abaqus for the structural side and FlowVision for the fluid side through a Direct Coupling interface. The definition of the problem as well the results of the simulation are presented in the paper.

### – Numerical 2D and 3D Methods for Computation of Internal Unsteady Pressure Field and Sound Near Field of Fans

Collaboration with:

CETIM, Noise and Vibration Center, France

INSA, Laboratory of Vibration and Acoustics, France

Abstract: Due to a current trend of increasing rotational speed and power, the problem of tone noise and pressure pulsation in centrifugal ventilators becomes a more urgent issue. Often the level of tones determines noise characteristics; mainly these are blade-passing frequencies (BPF).The broadband noise resulting from small-scale turbulent pressure pulsation in ventilators are undertaken using the method based on a representation of non-statonary motion of a compressible medium as a combination of acoustic and vortex modes.

### – Drop-Test” FSI simulation with Abaqus andFlowVision based on the direct 2-way coupling approach

Collaboration with:

Bureau VERITAS, France

Abstract: The paper presents a numerical simulation of the drop test in a still water for the multi-component box structure. The complexity of the problem is in the strong fluid-structure interaction (FSI) between the box and the water free surface. The numerical simulation of the drop test is performed with two software tools: Abaqus and FlowVision through the direct coupling interface, which manipulates, on the Abaqus side the Lagrangian finite-element mesh and on the FlowVision side the Eulerian finite-volume mesh with subgrid geometry resolution. The novel approach is that there are no auxiliary structure models (or 3rd party software) integrated in the applied software solution: the finite-element mesh is defined from the Cartesian CFD finite-volume mesh and allthe relationships between the CFD mesh cells and the outside FE faces are fully preserved. Each mesh node displacement is directly transferred between FlowVision and Abaqus, thus avoiding any additional interpolation.

### – Computational Study of Pressure Pulsation in a Medium Specific Speed Pump

Collaboration with:

InteRe Ltd

The centrifugal pump of high specific speed with a diagonal type of impeller flow is studied experimentally and numerically. 2D and 3D numerical methods are used with applying acoustics – vortex equations. Increasing energetic parameters of centrifugal pumps requires a more complex geometry of the impeller and volute as one need to raise the specific speed of the pump to provide a higher efficiency value. The pump of higher specific speed has an impeller with curved blades and diagonal meridional section. The flow outgoing the impeller has an essential axial component of velocity. Thus the two dimensional approach will not give the accurate prediction of pressure pulsations in the volute casing. This is why the new 3-dimensional method has been elaborated for this task. The 3D computational results of pressure pulsation are compared with those obtained by 2D computation. Measurements show that in the beginning of volute, in the pseudo-sound zone, amplitude of Blade Passing Frequency (BPF) spectral component is higher than that at the pump outlet by an order of magnitude. 3-Dimensional analysis gives a good agreement with experimental data while 2D prediction underestimates the BPF amplitude in the beginning of volute.

### – Oil Leakage Through a Valve Stem Seal

Collaboration with:

Dana Corporation USA

The simulation of oil leakage through a valve stem seal involves complex fluid-structure interaction between a moving valve stem (rigid body), oil and deformable seal (flexible body). In the simulation we used a full 3D model of a seal and considered a two-way fluid-structure coupling between the seal (structure) and oil (fluid). The seal deformation is modeled with Abaqus-explicit and oil leakage with FlowVision (finite volume based CFD code). The calculation domain is discretized by a volume Cartesian grid with dynamic local adaptation and uses a Euler grid approach for simulation of the moving boundary. At each physical time step the simulation domain is re-meshed and loads are exchanged between Abaqus and FlowVision(FV). Pressure values calculated by FV are transferred to Abaqus-explicit to calculate the resulting seal deformation. The data is automatically exchanged using Capvidia’s Multi-Physics-Manager (MPM). The MPM links FV with Abaqus and transfers data via Abaqus user-subroutines. The approach described above allows us to perform detailed analysis of the oil leakage through a valve stem for various engine loads and operational conditions. The oil seal shape and material can be optimized to minimize the oil leakage.

### – Experimental and Numerical Study of the Effect of Lateral Wind on the Feeder Airship

Collaboration with:

Vrije Universiteit Brussel

Feeder is one of the airships of the Multibody Advanced Airship for Transport (MAAT) system, under development within the EU FP7 project. MAAT is based on a modular concept composed of two different parts that have the possibility to join; respectively they are the so-called Cruiser and Feeder, designed on the lighter than air principle. Feeder, also named ATEN (Airship Transport Elevator Network), is the smaller one which joins the bigger one, Cruiser, also named PTAH (Photovoltaic modular Transport Airship for High altitude),envisaged to happen at 15km altitude. During the MAAT design phase, the aerodynamic studies of the both airships and their interactions are analyzed. The objective of these studies is to understand the aerodynamic behavior of all the preselected configurations, as an important element in the overall MAAT system design. The most of these configurations are only simulated by CFD, while the most feasible one is experimentally analyzed in order to validate and thrust the CFD predictions. This paper presents the numerical and experimental investigation of the Feeder “conical like” shape configuration. The experiments are focused on the aerodynamic force coefficients and the pressure distribution over the Feeder outer surface, while the numerical simulation cover also the analysis of the velocity and pressure distribution. Finally, the wind tunnel experiment is compared with its CFD model in order to validate such specific simulations with respective experiments and to better understand the difference between the wind tunnel and in-flight circumstances.

### – Influence of Interaction Between Oil and Rubber on Valve Stem Seal Oil Leakage

Collaboration with:

Dana Corporation USA

The valve stem seal is an important part of any internal combustion engine. The seal supplies a lubrication of valve stem and limits emission of oil. To design reliable and long-life stem seals a numerical simulation of the seal work is used. Numerical simulation helps to understand the main features of the stem seal working cycle and estimate the changing seal characteristics because of seal aging processes. The problem of oil flow via stem seal involves fluid-structure interaction between an oil flow induced by oscillating stem and deformable seal made from rubber. The Fluid-Structure Interaction Problem is solved numerically by using two codes: Abaqus/Explicit to get deformation of rubber seal and CFD code FlowVision to simulate oil flow. Both codes are two-way coupled by Multi Physics Manager. Simulation of the oil leakage through valve stem seal was studied for different engine rpm and for different rubber elasticity. Results from analysis show the strong dependence of the leakage on engine operating condition and elasticity of the rubber. Increasing engine speed and elasticity of the rubber result in increasing oil leakage through the seal. Moreover, increasing elasticity resulted in faster growth of the leakage with higher engine rpm. Also we found that during stem oscillation the rubber has complex motion. This motion results in wave-like changing of the clearance between the valve stem and the seal. Investigation of this effect allows predicting more accurately the properties of the valve stem seal.

### – Numerical Modeling of Air-Grass Flow and BPF Noise in Lawn Mowers

Collaboration with:

UNIPAT and MTD, Russia

The noise of domestic machines including lawnmowers becomes an urgent issue. As the technology matures, designers need better tools to predict performance and efficiency of these machines across a wide range of operating conditions and find optimal ways to reduce noise. Computational fluid dynamics is an increasingly powerful tool which enables designer to better understand all features of unsteady flow in these machines and to find optimal designs providing higher energetic characteristics, better cutting quality and lower pressure pulsation, vibration and noise. Cutting quality linked with evacuation of grass is a key lawnmower characteristic. Due to this fact application of two-phase (air-grass) lawnmower flow model is inevitable in a prediction procedure. The modeling procedure comprises determination of lawnmower average aerodynamic characteristics and CFD-CAA analysis by acoustic-vortex method to predict sound power data. This method is based on splitting the equations of compressible fluid dynamics into two modes – vortex and acoustic Computational approach applied for the vortex mode flow is a “moving body”- technique: The problem is solved in the absolute frame of coordinates and computational grid changes during the blade passing. Computations can be made in 4 stages: 1) Computation of the incompressible medium with getting average values of energetic parameters; 2) Computation of the incompressible medium for definition the source function of inhomogeneous acoustic-vortex wave equation; 3) Solution of the acoustic-vortex wave equation; 4) Computation of 2-phase flow. In the 3rd stage the pressure pulsation field can be represented like a sum of acoustic and vortex oscillation. Wave equation is solved relatively to pressure oscillation using an explicit numerical procedure. Zero pulsatory pressure is an initial condition for solution of the wave equation. The local complex specific acoustic impedance is used to define boundary conditions for the acoustical part of the pressure field. Thus the numerical procedure gives pressure pulsations field and sound power data on blade passing frequencies (BPF). For the 4th stage computations effective grass particle parameters are determined with accounting the stubble effect on flow parameters and particularities of grass particle interaction with rigid surfaces. Results of a lawnmower air-grass flow (grass particle trajectories and concentration) and corresponding BPF sound power data prediction are presented as an example of modeling procedure application.

### – **Coupled CFD and structural analysis for world ****outright sailing speed record preparations**

Collaboration with:

Verney Yachts, UK

Abstract: The brief for the boat, v-39 Albatross is to set a new world outright sailing speed record at Portland Harbor, UK by 2013. The boat is configured to add at least 10 knots to the current record by setting a speed above 65 knots (120 km/h). At speed the boat hulls will fly above the surface using a wing in ground effect. The pilot is able to sail on both port and starboard tack and can actively control the craft in speed, roll and height as well as direction.

Verney Yachts and Capvidia are carrying out transient Fluid Structure Interaction (FSI) simulations using Abaqus/Standard coupled with FlowVision-HPC from Capvidia. The objectives of the simulations described in this paper are to capture the above surface aerodynamics of the boat, and to establish overall aerodynamic forces and moments acting on the boat with different control inputs and boat speeds. Each FSI analysis involves capturing the movement of six independently rotating surfaces (four wing-sail surfaces and two outriggers), each surface able to freely weathervane into the local airflow. This process allows the control system to be tuned to minimize control cross coupling and to maximize forward thrust, whilst maintaining roll balance of the overall boat.

The work presented herein is being carried out alongside Computational Fluid Dynamics (CFD) analyses of the free surface hydrodynamics. The data generated will be pulled together into a final series of mathematical models to plot and analyze the forces and moments acting on the boat as the speed increases, mapping the way the boat will behave.

Keywords: CFD, Computational Fluid Dynamics, Transient, Coupled, Fluid-Structure Interaction, Speed Sailing, Sailing Speed Record, Wing-Sails, Wing In Ground Effect.