Numerical Simulation of MHD Jet flows

1
Numerical Simulation of MHD Jet flows
Kang Weishan
Southwestern Institute of Physics Chengdu,
610064, P R China
2
Outline

• Introduction
• Simplified Model
• Numerical Simulation
• Conclusion

3
1. Introduction

• free surface plasma facing components (PFCs)
• jet flow, droplet and film curtain

4
Advantages of free surface

• to withstand high plasma heat flux and ion flux
• to extract heat efficiently
• to improve thermal power conversion efficiencies
  significantly
• continuously renewable surface, to enhance
  diverter lifetime

5
2. Simplified Model
2.1 Governing equations

• conservation of mass
• conservation of momentum
• conservation of charge
• Ohms law

6
2.2 Schematic of jet flow
boundary layer
core zone
7
2.3 Analyses of induced electrical current and
potential
_
_


In x-y plane

• MHD effect on a jet flow can be broken into
  two parts
• in X-axle direction electromagnetic (EM) force
  tend to drag the flow, which leads to a shorter
  range distance and a lager radius of the jet flow
• in Y-axle direction EM force of the upper half
  part generally balances those of the lower half
  part, so the jet flow can keep stable and cross
  section is flatten

8
2.4 The cross-section of the jet flow is flatten
by EM force
9
3. Numerical Simulation

• The MHD effect is reflected in an additional term
  of Lorentz force in the momentum equation which
  is derived from the Ohms law by solving the
  electrical potential equation
• Volume of Fluid (VOF), which is used to track the
  interface between the phases and suited for free
  surface issues

10
3.1 Geometry and mesh of the computational model
11
3.2 Numerical result (1)
Induced electrical potential distribution in x-y
plane
12
3.2 Numerical result (2)
Induced electrical potential distribution in
cross-section
13
3.2 Numerical result (3)
x-component velocity distribution
14
3.2 Numerical result (4)
y-component velocity distribution
15
3.2 Numerical result (5)
z-component velocity distribution
16
4. Conclusions

• A jet flow under the gradient magnetic field can
  keep its shape stable due to EM force on its
  direction and the compressed EM force on its
  cross section
• Theres a decrease in the length of the range
  distance and an increase in the radius of the
  flow with the augment of the value of the
  magnetic field.
• Theres an increase in the length of the range
  distance of the flow with the augment of the
  value of the initial inlet velocity.

17
Thank you !