Computational Fluid Dynamics(CFD) – Basics & How it Evolved

CFD Effectiveness = Quality x Acceptance
where,
Quality – Fidelity of Data
Acceptance – Timeliness of Data

CFD should essentially meet 3 requirements:
I. Rapid Turnaround.
II. Reliable Accuracy.
III. Affordable Cost.

A typical design process includes:
i. Pre-conceptual
ii. Conceptual
iii. Preliminary
iv. Critical
v. Production

I. Linear Potential Methods

  • Solve 1st order PDE
  • Based on Prandtl-Glauert /Laplace equation.
  • Green’s Theorem
  • Surface Discretization
  • Vortex-Lattice Methods (VORLAX code). Mean surface representation of geometry & vortex filaments as singularities.
  • Panel Methods (Actual surface geometry discretized)
  • Purely Subsonic & Supersonic flows.
  • Good estimate of F & M and distributed air loads for steady-level flight.
  • 1960’s, established 1980’s.

II. Non-Linear Potential Methods

  • Solver 2nd order PDE
  • Based on Transonic Small Perturbation (TSP) or Full Potential Equation ( FPE).
  • Benefit of modelling transonic flows with Shocks.
  • Need to solve non-linear PDE’s.

III. Euler Methods

  • Highest level of Inviscid approximations.
  • Subsonic to Hypersonic regimes.
  • Captures Potential flow regimes (Wake sheds from wing & leading edges)
  • Solving atleast 4 and generally 5 coupled 1st order PDE’s instead of one 2nd order PDE.
  • 1980’s : Structured Grid Generation, Patched Multiblock, Overset Mesh
  • Mid 1980’s : Unstructured grid generation.
  • Convergence acceleration techniques- i) Local time-stepping, ii) Multi-Grid (FMG)
  • Explicit and Implicit time-marching schemes.
  • Time dependent equations
  • Codes didnot provide Total Drag (incl. Skin Friction) and thus N-S codes were pursued in parallel.

IV. Navier-Stokes Method

  • Same equation except the diffusion terms in N-S solver
  • Elimination of the diffusion term converts the N-S equations to Euler equations as they both share some convective terms.
  • RANS- Turbulence Model – Simple algebraic model to sophisticated Reynolds’ Stress model.

‘Dynamics and Control of Tactical Missile System with Morphing Wings’ – A Synopsis

The field of Aerospace Technology, both in military and commercial aviation has evolved in the last 100 years since Wright Brothers’ maiden flight from Kitty Hawk in 1903. In the turn of a new century and the recent interest in a field which has been in existence since Wright Brothers’ wing warping concept,a new form of wing warping, called Wing Morphing can truly change the way we perceive the overall aerodynamic design, control and guidance philosophy in missile technology.

When paired with evergrowing computer technology, active materials, the wing morphing concept holds the potential to make future missile design more efficient, lighter, less complex and even safer with low observable qualities which is set to become a game-changer for stealth combat aerospace vehicles. Morphing wings concept can drastically reduce flying wing’s reliance on jointed control surfaces and eventually eliminate the need for traditional control surfaces all together. This will be applicable for any future stealthy airfames, including missiles, unmanned combat air vehicles, multi-mission fighter aircrafts.

Designs with morphing wings can significantly change the aerodynamics dramatically for high performance maneuvers, loitering, high altitude and low altitude flights. Traditional actuators will not suffice the complexity the morphing wing brings to the overall design. A different flight control system is required, one which is analytically, numerically and experimentally proven and acquires the dynamic model of the morphed surface and performs real-time tuning of the controllers. A morphing wing designed for a missile would optimally be capable of changing its sweep and span simultaneously, in order to provide superior roll moment to conventional missile control fins.

As almost all currently designed tactical missiles are centred on conventional fixed planform arrangement, the consideration for morphing concept in tactical missile systems calls for investigation into several exciting research areas, including aerodynamic modelling, non-rigid dynamics and flight control systems.

15 Ph.D. Essential Pointers!

This is my list of essential PhD pointers to go through the journey while pursuing PhD, irrespective of the field. Do something NEW. Make a Plan ; To-Do List. 3-4 years of dedicated Research. Make year-to-year plan; Break it up in monthly/yearly plan. Celebrate your success in between; Intermediate goals. Keep your supervisor updated..keep him … Continue reading “15 Ph.D. Essential Pointers!”

This is my list of essential PhD pointers to go through the journey while pursuing PhD, irrespective of the field.

  1. Do something NEW.
  2. Make a Plan ; To-Do List.
  3. 3-4 years of dedicated Research.
  4. Make year-to-year plan; Break it up in monthly/yearly plan.
  5. Celebrate your success in between; Intermediate goals.
  6. Keep your supervisor updated..keep him posted.
  7. High Impact Journals.
  8. Be meticulous, diligent and honest to yourself.
  9. Listen to the feedbacks you receive.
  10. Document your work.
  11. Publish 4-5 journal papers; or Write a Book.
  12. Go to Conferences.
  13. Be visible; Don’t be backstage and don’t shy away.
  14. Have Fun at your research.
  15. Read Journals.