Studies on Shock Waves Produced by Reddy Tube

Under the guidance of Mr. Nagesh

Naveen T 1AT11ME065Prashanth Madankar 1AT11ME070Sarvesh Nagashetty 1AT11ME085

Vinay M Y 1AT11ME098

Atria Institute of Technology

ABSTRACT

•In this project we will be studying the shock waves in Reddy tube and increase its strength using mechanical

lenses.

• Computational Fluid Dynamics (CFD) will be used to arrive at optimum configurations for focusing shock

waves and the best configuration will then be experimentally tested.

MACH NUMBER AND FLOW REGIMES

•The ratio of the speed of a moving object (u) to the speed of sound (c) in a fluid gives rise to one of the most

important dimensionless quantities in the field of aerodynamics. The ratio is known as the Mach number (M) in

honor of Ernst Mach (1838–1916), the Moravian physicist, psychologist, and philosopher who studied sound and

ballistics.

M=u/c

•If the Mach number is less than 0.8, it is known as subsonic flow.

•If the Mach number is between 0.8 and 1.2, it is known as transonic flow.

•If the Mach number is greater than 1.2, it is known as supersonic flow.

•If the Mach number is greater than 5, it is known as hypersonic flow.

SHOCK WAVES

• Shock waves are mechanical waves of finite amplitudes and arise when matter is subjected to

rapid compression.

Conical shock waves around a jet plane made visible by condensation

• These are produced by sudden release of energy (like in explosions or volcanic

eruptions) by bodies moving at supersonic speeds or by impact of high speed

projectiles or by laser ablations.

• Like an ordinary wave, a shock wave carries energy and can propagate through a

medium. It is characterized by abrupt change in pressure, temperature and density of

medium.

APPLICATIONS OF SHOCK WAVES

•Needle-less drug delivery system.

•Lithotripsy.

•Design of bomb suits.

•Preservative impregnation into wood.

•Oil extraction from hard wood, medicinal plants and oil seeds.

•In genetic transformation where a DNA is introduced into the cell without damaging the living cell.

•To remove micron size dust particles from silicon wafer surfaces.

•In material science.

•High temperature chemical kinetics.

SHOCK TUBE•A shock tube is a simple device that is used to generate a shock wave in a controlled environment.

•The schematic of a shock tube is given in figure. It consists of a driver section and a driven section separated by a diaphragm. The pressure in the driver section of the shock tube will be increased to rupture the diaphragm creating a shock wave in the driven section. The strength can be represented by “Mach number”.

REDDY TUBE

Schematic diagram of the 29mm diameter Reddy tube indicating the locations of pressure sensors. b. Photograph of fully assembled, modified Reddy tube with pressure gauges mounted for measuring the shock speed and the diaphragm rupture pressure

•It is a hand operated shock producing device.•It operates on the principle of free piston driven shock tube (FPST).•It is capable of producing Mach number exceeding 1.5.•The rupture pressure is a function of the thickness of the diaphragm.•Temperatures as high as 900K can be easily obtained by the Reddy tube

WORKING OF REDDY TUBE

•It consists of a 29 mm inner diameter stainless steel tube divided into a 490 mm long driver section and 500 mm

long driven section separated by a diaphragm.

•The diaphragms used in this Reddy tube are made of 0.1 mm thick aluminium/ 90-95 grade tracing paper.

• Rupture pressure can be varied by varying the number of foils paced at the diaphragm station.

• The diaphragm rupture pressure in the driver section is generated manually by pushing a 29mm diameter

piston.

•This rupture pressure is monitored using a digital pressure gauge mounted close to the diaphragm station.

• The speed of the shock wave inside the driven section is measured using the pressure jump obtained at the two

piezoelectric pressure gauges.

COMPUTATIONAL FLUID DYNAMICS (CFD)

•Computational Fluid Dynamics (CFD) has emerged as a complementary tool for studying fluid flows, wherein

the governing equations of fluid dynamics are solved using numerical techniques typically with a computer

program.

•In this study a commercial code ANSYS-CFX will be used. The first step in CFD is to generate the geometry of

the flow domain model.

•Then, the domain is divided into a number small volumes (called “Mesh”).

• The initial and boundary conditions are setup and the governing equations are solved.

•ANSYS-CFX uses a coupled multi grid algorithm for solving the discretized fluid flow equations which are

important to get stable solutions for complex flows such as the ones generated in the shock tube. The CFD code

will first be validated for predicting the flow in the Reddy tube.

•Configurations to focus the shock wave will be devised and these configurations will first be studied using CFD

and the best of these configurations will be experimentally tested in the Reddy tube.