Research and Development

1. Shock wave Interaction in Magneto-hydrodynamics Environment
Magneto hydrodynamics (MHD) is the study of the behavior of conducting fluids like plasma under the action of magnetic field. Sun acting as a giant dynamo has poloidal magnetic field lines with the rotation of the plasma, an electric field is generated which in turn gives rise to an induced magnetic field. This induced magnetic field distorts the original magnetic field of the sun and the field lines becomes 'literally frozen' in the plasma which gives rise to various astronomical phenomenon like sunspots on the photosphere of the sun, coronal mass ejection, solar flares etc. The governing equations of MHD can be represented as the coupled equations of Euler's equations of hydrodynamics with Maxwell's equations of electromagnetics. Astrophysical plasma is assumed ideal in nature due to its electrons collision less flow, hence MHD equations are devoid of viscous and resistive terms. There are certain difficulties in solving these equations, due to its non-convex nature the waves speed may coincide, which gives rise to compound waves in which the rarefaction wave is attached with the normal shock wave. There is also formation of monopoles in multidimensional problems due to the numerical error associated with the schemes. These complexities make it difficult to solve MHD equations with numerical techniques like Lax-Wendroff or Mac-Cormack. To remove high oscillations, they are solved with high resolution schemes like TVD with Gudonov's 2nd order. Higher order reconstruction schemes, Essentially Non-Oscillatory (ENO) & Weighted Essentially Non-Oscillatory (WENO) schemes are applied for higher accuracy. Generally this reconstruction takes ample amount of computational costs. In this present work the component wise higher order reconstruction is applied with hybrid weighted flux scheme to minimize the computational costs. The numerical scheme is applied on number of problems including Euler's and MHD equations. The hybrid scheme is thus validated and has been compared with the results of the FLASH code. Additionally PISO algorithm is tried on MHD equation in OpenFoam environment in this present work.

Density plot at 0.1 Sec and 3.0 Sec

Density plot at 0.1 Sec and 3.0 Sec

This work carried out by Mr.Ved Mukherjee (ME) under the guidance of Dr. Deore N.R.

2. Numerical Simulation of Uneven Heating of Missile Surface Traveling at Supersonic Speed
Ballistic missile travels at very high speed, in which the viscous heating over surface encountered a major problem. At this speed, fluid particle transfer the kinetic energy of particle into heat and exchange their momentum with wall of missile. The unsteady flow around the Missile is studied for predicting the aerodynamic performance. The numerical study focuses on the flow over missile at different angle of attack. During interaction of fluid with the missile body, the friction forces are dominant on windward side as compare to the leeward side, which results into uneven heat generation. This viscous heating causes the uneven temperature distribution over missile. The presented study estimates the heat transfer rate and temperature distribution on 2D and 3D missile surface. The numerical study is carried out using SST k-w model over Missile L/D ratio = 10, Length = 4 m, Diameter = 0.4 m. The temperature distribution and pressure variation on the missile surface at supersonic speed (Mach 3) is discussed. Numerical study shows that, leeward side separation takes place which result into decrease in temperature from 823 K to 450 K, as the AoA increases. Difference in temperature distribution over missile is 390 K at AoA 20o. Directional deformation is increases from 0.7327 to 1.7175 mm as AoA increases from 12o to 20o. It implies that obtaining cruise performance is very essentials to get efficient aerodynamic performance. Total deformation is increases from 11.041 to 24.979 mm as AoA increases 12o to 20o.

Temperature Distribution over Missile Surface at AoA 8o.	Temperature Distribution over Missile Surface at AoA 20o.	Directional Deformation by FSI at 12o.
Directional Deformation by FSI at 20o./p>

Work carried out by Mr.Kishor Gajanan Malokar (ME) under the guidance of Dr. Mahesh M.S. (DIAT) and Dr. Deore N.R. (PCCoE)

3. Heat Flux Estimation on the Missile Base at High Altitudes and Supersonic Speeds
This project was motivated by the problem of losing connectivity of missile with the control station. The reason behind this was damaging of electronic sensors due to overheating at he missile base. Generally as we move go up in the atmosphere there is decrease in atmospheric pressure, which leads to expansion of exhaust plume coming out from Missile nozzle as shown in Fig. 1. This expanded hot exhaust gases transfers its heat to the base of material. This project was aimed to estimate the heat flux on the missile base travelling at supersonic speeds (Mach 3) and at high altitudes numerically with help of simulation software.

Expansion of exhaust plume at different higher altitudes

High temperature across the base of missile shown in temperature contours Fig. 2. It is observed that temperature on the base increases with increasing altitudes. After going from 80 Km to 90 Km, a drastic change in temperature from 850 K to 2870 K and heat flux variation was observed from 145 Kw/m2 to 350 Kw/m2. Maraging steel has melting temperature of 1686 K and hence it was suggested that missile moving above 80 Km must provide proper insulation in order to keep safe the electronic sensors installed near the base.

Expansion of exhaust plume at different higher altitudes

Work carried out by Mr.Birendra Kumar Rajan (ME) under the guidance of Dr. Mahesh M.S. (DIAT) and Dr. Deore N.R. (PCCoE)

4. Aero-acoustic modeling of radiator fan Axial fan used inside radiator is a major source of noise generation inside the generator. Now a day's Gensets have to meet noise limits in different parts of the world, such as Central Pollution Control Board of India's (CPCB-II) norms in India or European Commission's (CE) Regulation (2000/14/EC). For developing gensets to meet such noise limits, it is important to develop more accurate noise levels prediction tools before manufacturing Gensets. To address the experimental challenges, a numerical analysis of noise prediction by using Ffowcs Williams and Hawkings method was performed.
Computational Fluid Dynamics (CFD) codes are used to capture the pressure fluctuation generated by the source. This pressure fluctuation is responsible for the noise generation. The transmission of sound waves in air medium is taken care by wave equation. This wave equation is derived using simple principle of mass and momentum conservation equation and the time based information is transformed to frequency based using Fast Fourier Transformation (FFT).

Expansion of exhaust plume at different higher altitudes

Tonal noise at Blade Pass Frequency and next respective harmonics are captured at radial receiver locations in transient simulation. Power Spectral Density Spectra as shown in fig 3; shows that tonal noise is much more dominant in low frequency region below 400 Hz frequency; therefore fan surface emitting higher SPL (dB) in this lower range should be modified. Surface pressure level contours at fan surface shows dominating area of noise generation. In low frequency region below 400 Hz frequency dominating source regions are i.e. blade suction surface tip, trailing edges, and hub sections. Modifications of these regions are required to be done to reduce noise.

Overview of the Acoustic analogy model

Work carried out by Ms.Sumedha Mohod (ME) under the guidance of Mr.Potdar U.G. and Dr.Deore N.R.

5. Experimental Investigation of Lifted Spray Flame with Preheated Co-flow Condition Liquid fuel currently provides the energy used by a variety of power systems such as industrial furnaces and boilers, as well as automotive and aerospace engines. Understanding the physical phenomena that control spray combustion processes is important because, as most of the practical combustion devices initially apply the fuel as a multi-phase flow. Applications such as industrial furnace, small capacity boilers, jet propulsion, and gas turbine combustion all utilize liquid fuels. This broad application motivates a fundamental research of the mechanisms that control spray flame behavior. Issues such as flame structure, stabilization, and blow-off condition are important aspects of spray combustion that has to be understood for the wide variety of combustors that exist. In the present study, experimental work has been carried out for three different cases i.e. No coflow condition, normal coflow condition and preheated coflow condition. It has been observed that the flame lift-off is directly proportional to injection pressure, spray ejection velocity, mass flow rate of fuel and coflow velocity but inversely proportional to coflow temperature. Spray injectors are used to inject fuel with mass flow rate varies from 1.8 Kg/hr to 7.4 Kg/hr.

Experimental Setup of Lifted Spray Flame

Average Velocity Distribution of Non-reacting Kerosene Spray with Co-flow air

Investigation of variation of lift-off height of spray flame is carried out for three cases i.e. 1) No co-flow condition 2) Co-flow Condition and 3) Preheated Co-flow condition. It is observed that the lift-off height increases with increasing in injection pressure and increasing in co-flow velocity, and decreases with co-flow temperature. At higher co-flow velocity the flame get blow-off but with preheating the blow-off condition is minimized.

Injection Pressure vs LOH

Co-flow Velocity vs LOH

Work carried out by Mr.Kapil Sawankar (ME), at IIT Bombay, under the guidance of Mr.Potdar U.G.