MEEN 5301-Computational Fluid DynamicsGroup-3

Study and Analysis of Shock waves on Re-entry Capsules using Fluent and determining the best design

Lamar UniversityDepartment of Mechanical Engineering

Likhith NalluriVijay Teja BangiNijammudhin Imrani

Abstract The scientific and technological advances of twentieth century allowed the mankind to push the

boundaries far beyond the Earth’s atmosphere in to space. Thus began exploration of nearby planets for habitable environment.

The gravity and atmosphere of the planet causes an incredible stress on the spaceflight during entry because of atmospheric drag and aerodynamic heat. This project deals with the CFD analysis in ANSYS FLUENT of the entry capsule with payload in to the atmosphere of the planet Earth.

The shock wave behavior during the entry of the module will be analyzed. The report is aimed to choose the best design of capsule which reduces the formation of dangerous shock waves.

• Its is a part of a space craft which are used for space exploration applications.

• Re-entry refers to the movement of the manmade objects to any planet’s atmosphere from the outer space

• They are especially designed to withstand high heating loads during the re-entry phase

Re-entry capsule

• Re-entry motion can be analyzed considering it as a dynamic problem, with a reference frame as re-entry system

• Vehicles center of mass at the start of re-entry is considered as the reentry coordinate system origin

• Following Forces affect the capsule i) The force of gravityii) The force of dragiii)The force of lift

• Drag force resists motion through the atmosphere . It acts in the direction opposite to your motion.

• Lift force produced at a right angle to the direction of motion as a result of air moving over an object's surface. An object with the aerodynamic shape will generate enough lift force to overcome the force of gravity and lift the vehicle into the air

Re-entry motion

Shock wave• Shock wave results when air molecules bounce off

from front side of the high speed vehicle and then collide with the incoming air.

Depending on the vehicle’s shape, the shock wave can either be attached or detached.

If the vehicle is streamlined (high BC, like a cone), the shock wave may attach to the tip and transfer a lot of heat, causing localized heating at the attachment point.

If the vehicle is blunt (low BC, like a rock), the shock wave will detach and curve in front of the vehicle, leaving a boundary of air between the shock wave and the vehicle’s surface.

Designs

Models • The K-epsilon model is one of the most common turbulence model

• It is a two equational turbulence model, that means, it includes two extra transport equations to represent the turbulent properties of the flow.

• The RNG model was developed using Re-Normalisation Group (RNG) methods by to renormalise the Navier-Stokes equations to account for the effects of smaller scales of motion

Shock waves There are different types of shockwave : Attached shockwave Detached shockwave Moving shockwave Detonation shock wave

Comparison of Static Temperature

Comparison of Velocity Magnitude

The values of the colors green and red which are at the inlet in the two pictures are same

Comparison of Entropy

The values of the colors green and blue which are at the inlet in the two pictures are same

Comparison of Static Pressure

The values of the colors red and blue which are at the inlet in the two pictures are same

Discussion Blunt shock waves are more preferable than oblique shock waves because

the oblique shock waves will increase the effects of parameters like velocity, temperature, pressure on the surface of the Reentry capsule compares to blunt shock waves.

Due to increase in the parameters, the heat transfer through the capsule will also increase and damage the foam under the thermal shield which is extremely dangerous for the capsule.

Hence most of the space vehicles which are reentering the earth’s atmosphere are designed in the shape of blunt profile to reduce the effect of forming oblique shock wave which will danger the capsule.

The CFD analysis of our models proves the same point.