PRODUCTS   VorTran-M Wake Module

VorTran-M Wake Module - Couples to CFD Solutions to Preserve Vorticity

Accurate performance prediction is essential to the development, design and analysis of rotorcraft. While current numerical analysis tools can, in principle, model complete rotorcraft, in practice these implementations are severely hampered by accuracy limitations broadly attributed to modeling assumptions (e.g. vortex core models in Lagrangian methods) or numerical deficiencies (e.g. excessive numerical diffusion for Eulerian CFD). Thus, commonly used analysis tools fail to predict adequately the unsteady wakes and load distributions of rotor and fuselage designs. An approach that combines the first-principles physical modeling capability of Eulerian schemes with the vortex preservation capabilities of Lagrangian vortex techniques has long been needed. Enabled by breakthrough technologies in Eulerian wake modeling [1,2] that specifically address the critical numerical diffusion issue, the VorTran-M wake module is a first-principles Eulerian vorticity transport wake module that provides an unprecedented ability to capture the true temporal and spatial structure of the rotor wake when coupled to a wide range of CFD (both Eulerian and Lagrangian) tools [3].


Schematic of VorTran-M-CFD coupling


Rotor wakes calculated with the VorTran-M module coupled to an unstructured Navier-Stokes solve hover (left); high speed forward flight (right).


While originally designed to address the numerical diffusion of vorticity associated with the simulation of rotorcraft wakes, this model is equally capable at modeling other vortex-dominated flows such as those associated with ship airwakes, road-vehicles and other bluff bodies [4]. In addition, the multiple domain capability makes the VorTran-M module particularly adept at simulating interactional flows such as those in ground effect, formation flight, flight into "urban canyons", terminal area operations and dynamic interface (ship airwake-rotorcraft wake interactions) operations [5].

For more information on licensing the VorTran-M module contact Glen Whitehouse at CDI 609.538.0444 ext 126.


Ship (simple frigate shape) airwakes calculated with VorTran-M module coupled to an Euler solver


Bluff-body type wake calculated with the VorTran-M module coupled to an unstructured Navier-Stokes solver


Recent work coupling VorTran-M to the NASA CFD solver OVERFLOW has demonstrated the ability of the module to enhance current state-of-the-art primitive variable solvers [6]. Predictions of the Caradonna and Tung hovering rotor experiments [7] demonstrate that hybrid OVERFLOW/VorTran-M is capable of producing more accurate predictions of integrated thrust, spanwise loading and wake trajectory, all with lower cost, than conventional OVERFLOW calculations.


Comparison of measured and predicted spanwise loading for the Caradonna and Tung hovering rotor experiments


Comparison of measured and predicted tip vortex trajectory for the Caradonna and Tung hovering rotor experiments. Vertical position as open symbols and radial location as filled.



KEY FEATURES

  • Explicitly conserves vorticity
  • Prevents the spatial smearing of vorticity with an innovative Riemann solver
  • Employs fast Biot-Savart / Poisson solvers and variable resolution adaptive grid techniques
  • Can be coupled to a wide array of Eulerian (such as structured, unstructured and overset) solvers and Lagrangian (such as vortex-lattice, free-wake and panel) flow models.
  • Supports multiple CFD domains

For more information about licensing VorTran-M contact Glen Whitehouse at CDI 609.538.0444 ext 126.


REFERENCES

  1. Brown, R.E., 2000, "Rotor Wake Modeling for Flight Dynamic Simulation of Helicopters", AIAA Journal, Vol. 38, No. 1, pp. 57-63.
  2. Brown, R.E. and Line, A.J., 2005, "Efficient High-Resolution Wake Modelling using the Vorticity Transport Equation", AIAA Journal, Vol. 43, No. 7, pp. 1434–1443
  3. Whitehouse, G.R., Boschitsch, A.H., Quackenbush, T.R., Wachspress, D.A. and Brown, R.E., 2007, "Novel Eulerian Vorticity Transport Wake Module for Rotorcraft Flow Analysis," 63rd Annual Forum of the American Helicopter Society, Virginia Beach, VA.
  4. Whitehouse, G.R., A.H. Boschitsch, M.J. Smith, C.E. Lynch, and R.E. Brown. "Investigation of Mixed Element Hybrid Grid-Based CFD Methods for Rotorcraft Flow Analysis." 66th Annual Forum of the American Helicopter Society. 2010. Phoenix, AZ.
  5. Keller, J.D., G.R. Whitehouse, A.H. Boschitsch, J. Nadal, J. Jeffords, and M. Quire. "Computational Fluid Dynamics for Flight Simulator Ship Airwake Modeling." Interservice/Industry Training, Simulation, and Education Conference (I/ITSEC) 2007. 2007. Orlando, FL.
  6. Whitehouse, G.R. and H. Tadghighi. "Investigation of Hybrid Grid-Based CFD Methods for Rotorcraft Flow Analysis." AHS Specialist's Conference on Aeromechanics. 2010. San Francisco, CA.
  7. Caradonna, F.X. and C. Tung, "Experimental and Analytical Studies of a Model Helicopter Rotor in Hover." Vertica, 1981. Vol. 5: p. pp. 149-161.