Actiflow: Using OpenFOAM Technology for Aeroconsulting

Transcription

1 Actiflow: Using OpenFOAM Technology for Aeroconsulting Delft, November 4 th 2010 OPENFOAM is a registered trade mark of OpenCFD Limited, the producer of the OpenFOAM software

2 Today the following items will be presented to you Actiflow: an engineering company with a focus on aerodynamics The reasons why Actiflow chose OpenFOAM as the main CFD solver Examples on the use of OpenFOAM by Actiflow Development of steady state electrohydrodynamics solver ehdfoam Active automotive aerodynamics Other examples of the use of OpenFOAM within Actiflow Introducing CFDDesk, the Dutch OpenFOAM support system Concluding remarks on OpenFOAM technology as used within Actiflow 2 25

3 Actiflow is an engineering company with a focus on aerodynamics Actiflow is founded in 2005 as a spin-off of Delft University of Technology We offer various services: Design Engineering (including prototyping and testing) Aero Consulting 3 25

4 Actiflow is young and dynamic, providing accurate and fast results Actiflow is flexible and thinks with the customer We are experienced in a large range of fluid flow problems We can perform several tasks in the design and prototyping phases and assist product development Next to computational facilities we also have experimental facilities in our workshop 4 25

5 Actiflow chose OpenFOAM technology based on several characteristics OpenFOAM is open source and allows parallel calculations without licensing costs OpenFOAM is, generally speaking, as accurate as or even better than commercial CFD codes Solvers can be modified for specific needs Special boundary conditions and applications can easily be created and implemented Full control over the solving algorithms without hidden filters and limiters Large amount of models, algorithms and solvers are available State of the art development work is going on all around the world Assistance with common problems via the forum 5 25

6 A solver for steady-state electrohydrodynamics, ehdfoam, was created in order to model an innovative air purifier For one of the customers, Virus Free Air (VFA), a new solver had to be created Their innovation is an electric air purifier based on corona wind There was a need to compute the flow of charged particles in the design stage of the electronic air purifier In order to model this flow a solver was created based on available solvers: electrostaticfoam and simplefoam To model the corona wind effect a new boundary condition, corona discharge boundary is created: Several types are created, depending on the application and conditions For post-processing the Lagrangian particle solver was modified to the electrostaticparcelfoam, which calculates particle paths of charged particles in an electrically charged fluid influenced by electrostatic forces, gravity, buoyancy and drag 6 25

7 ehdfoam, solver for steady-state electrohydrodynamics Corona discharge is defined as the electrical discharge brought on by the ionization of a fluid surrounding a conductor, which occurs when the electric field strength exceeds a certain value. Source: N. E. Jewell-Larsen et al., Modelling of corona-induced electrohydrodynamic flow with COMSOL Multiphysics, ESA Annual Meeting on Electrostatics,

8 The model uses these equations, involving two-way coupling of fluid and electric field u = ( ) 2 u u = + ν + ν t u + ρce ν t 2 = 0 p ρ from turbulence model Electrostatic body force 1 ρ ρc V ε 0 J = E + u + D = ( ρ ) C µ e ρc ρc 0 Continuity Momentum Turbulence Modeling Gauss law Conservation of charge 8 25 Convection of charge density

9 The model equations are implemented in ehdfoam as follows Pressure-velocity coupling uses the SIMPLE algorithm Turbulence is modeled using the OpenFOAM RAS models Electrostatic equations are solved before the SIMPLE loop 9 25

10 The electrostaticparcelfoam model equations are defined similarly s' = t s= s' Fp ( s) xp ( t) = x + p ( u ' 0 + p ds ds 0 m s' = 0 s= 0 p F = F + F + F + F p D E g b 2 ρcd ( Re) π r FD = ( u p u ) u p u 2 FE = Eq p F = m g g p 4 3 Fb = π rp ρg 3 Location of particle Forces acting on the particle Aerodynamic force (drag only) Electrostatic force Gravitational force Buoyancy force Particle charge needs to be determined 10 25

11 The electrostaticparcelfoam model equations are defined similarly q πε r E 2 max = 4 0 p qmax q( t) = τ 1+ t 4ε 0E τ = J * qτ t = q q max q qmaxτ = t + * ( t τ ) 2 Saturation charge Current charge, if q(0)=0 Time needed to reach 0.5 q max from q(0)=0 Substitution, q(t*)=0 (definition) New time derivative to be used 11 25

12 The first test case was a 2D Wire Flow Validation of the solver, comparison with an experiment and simulation with COMSOL (N. E. Jewell-Larsen et al., Modelling of corona-induced electrohydrodynamic flow with COMSOL Multiphysics, ESA Annual Meeting on Electrostatics, 2008) Single coronating wire with 14 collecting wires Coronating wire potential: 8000 V Collector wires potential: 0 V Jewell-Larsen et al. ehdfoam 12 25

13 The results of the test case are satisfactory The final goal of the solver is accurate prediction of the flow field due to corona discharge The solver recreates the electric, charge density and velocity fields that were observed in the paper during computation and experiment Jewell-Larsen et al. ehdfoam 13 25

14 The solver and postprocessing utility where later applied to an actual design The objective of the solver was an actual application of corona wind in an air filter Challenging 3D Case: very small needles, rather large domain Circular tube, with carefully placed needles Movie shows charged particles enter a filtering tube and how they are affected by the electric and velocity fields Air is sucked into the tunnel due to corona discharge effect Particles are effected by the charged needles and secondary flow is induced 14 25

15 The base of Actiflow is automotive application of active aerodynamics Actiflow applied boundary layer suction on: Formula Renault front wing Ferrari F430 diffuser Using OpenFOAM, Actiflow simulated boundary layer suction on: Bluff body equipped with a diffuser Ahmed Body Several commercial car models Using OpenFOAM, Actiflow simulated base bleed on: Ahmed Body VW Golf V Several other commercial car models 15 25

16 A procedure for active aerodynamics analysis was developed The procedure starts with analysis of the flow around the standard geometry The flow field is investigated and the geometry is adapted for base bleed and suction panels Without flow control, the simulation is carried out again, to check the consistency Active flow control simulations are carried out to find promising configurations 16 25

17 Results obtained with the Ahmed body are promising With a parameter variation, the configurations can be optimized for drag reduction or lift reduction/downforce increase Using an optimal design the lift of the body can also be influenced positively Finally there are geometrical design loops incorporating the active flow control system 17 25

18 OpenFOAM results for active automotive aerodynamics are within engineering accuracy and fast Remarks considering the accuracy of the results are the following: The correct trends are captured No cooling flow, simplified wheels, cleaned geometry Simulation of bluff body flow remains challenging for RANS Actiflow is investigating LES/DES, but it is not yet applicable in design loops Simulations are good for conceptual design, road/wind tunnel tests are used for the final design 18 25

19 Actiflow is active in different fields of application Our main fields Automotive Wind Energy Building Physics Medical Other 19 25

20 Actiflow uses OpenFOAM for several other flow phenomena Building Physics: Wind hindrance HVAC design Office Buildings Church renovation (Conjugate) Heat transfer Heat flux sensor design Heat transfer with floor heating Medical solutions Innovative infant incubator Wind energy Development of small wind turbines Active flow control on large scale wind turbines 20 25

21 Actiflow uses OpenFOAM for several other flow phenomena Ship hydrodynamics: Investigation into the occurrence of cavitation Turbomachinery: Pumps, ventilation systems Consumer goods: Senz Umbrellas Smoke and toxic contents dispersion Welding smoke: Clean Air Diesel generator exhaust fumes Factory planning 21 25

22 Setting up Dutch OpenFOAM support desk for other companies Together with Vortech, Actiflow offers the possibility to set-up OpenFOAM support for other companies Several levels of support will be created First line support: Fast response for small problems (telephone/ ) Second line support: In depth analysis of the problem, may take more time Consultancy is another option: We help decide whether the use of OpenFOAM is beneficial Support with installation, updating and organization Development of solvers and utilities for specific problems Advice on model choice and solution method With the experience of Vortech and Actiflow, the steep learning curve becomes more gentle The support system is still young, so any comments will be appreciated More information can be gathered at Vortech s and our stand and in the flyer 22 25

23 The website will be used as a portal for support and is online

24 Concluding remarks on the use of OpenFOAM for aeroconsulting Due to the versatility of OpenFOAM, Actiflow can consult a large variety of customers After several years of experience we have confidence in our simulations and the solutions to problems we solve The open source format allows to create or adapt models as needed and helps understanding the working method of the software With OpenFOAM we can accurately solve complex problems from different fields within the timeframe of an engineering design process With our experience we can help others start enjoying the many benefits of OpenFOAM 24 25

25 Actiflow BV Zinkstraat AD Breda The Netherlands Tel: