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Topic : PraVaHa

GS-3 Mains  : Science and Technology

Revision Notes

 

ISRO’s Vikram Sarabhai Space Centre (VSSC) has made a significant breakthrough with PraVaHa, a powerful Computational Fluid Dynamics (CFD) software. PraVaHa stands for Parallel RANS Solver for Aerospace Vehicle Aero-Thermo-Dynamic Analysis.

What it Does:

PraVaHa simulates airflow (both inside and outside) across various aerospace vehicles, including launch vehicles, winged aircraft, and non-winged re-entry vehicles. This simulation capability is crucial for designing efficient and safe spacecrafts.

Key Applications:

• Gaganyaan Program: PraVaHa played a critical role in analyzing the aerodynamics of the Human-rated Launch Vehicle (HLVM3), Crew Escape System (CES), and Crew Module (CM) for the Gaganyaan mission. This ensures the safe flight of India’s first astronauts.

Technical Capabilities:

• Flow Simulation: PraVaHa can handle airflow simulations under various atmospheric conditions, considering both ideal gases and real gas behavior (which is more complex and realistic).
• Advanced Validation: Ongoing validation efforts aim to enable PraVaHa to simulate complex chemical reactions, such as those occurring during air dissociation at Earth’s re-entry or within scramjet engines.
• Unsteady Aerodynamics: PraVaHa tackles unsteady aerodynamic challenges, which are essential for understanding airflow behavior around rocket bodies and the resulting acoustic noise generated during flight.

Impact on Aerospace Design:

• Optimized Designs: PraVaHa allows engineers to evaluate numerous design configurations during the initial stages of launch vehicle development, leading to more efficient and streamlined spacecrafts.
• Predicting Loads: By simulating airflow, PraVaHa helps predict the aerodynamic and thermal loads experienced by vehicles during launch and re-entry. This information is critical for designing the vehicle’s shape, structure, and Thermal Protection Systems (TPS) to withstand these extreme conditions.
• Noise Reduction: PraVaHa aids in understanding and mitigating acoustic noise produced during missions, contributing to a smoother and more comfortable spaceflight experience for astronauts.

Future of PraVaHa:

With its ongoing development and validation, PraVaHa is poised to become an even more powerful tool for ISRO, enabling the design of next-generation space vehicles with superior performance, safety, and efficiency. This will be instrumental in India’s future space exploration endeavors.

 

 

Additional Notes

 Computational Fluid Dynamics (CFD)

CFD: Unveiling the Secrets of Fluid Flow

CFD, or Computational Fluid Dynamics, is a powerful tool used to analyze and predict the behavior of fluids – liquids and gases. By leveraging numerical methods and algorithms, CFD helps engineers and scientists understand how fluids move and interact with their surroundings in various situations. This knowledge is crucial for numerous industries, including:

• Aerospace: Design airplanes, rockets, and spacecraft with optimal aerodynamics and heat transfer.
• Automotive: Improve vehicle fuel efficiency, thermal management, and comfort through better aerodynamics.
• Civil Engineering: Analyze wind loads on buildings, design efficient HVAC systems, and model environmental impact.
• Marine Engineering: Optimize ship hulls, assess fluid-structure interaction for offshore structures, and analyze submarine hydrodynamics.
• Biomedical Engineering: Simulate blood flow for medical research and device design, model airflow in lungs to understand respiratory conditions, and optimize medical devices.

A Historical Journey Through CFD

The journey of CFD began in the 19th century with the development of fundamental fluid dynamics equations, like the famous Navier-Stokes equations. These equations govern the motion of fluids. The 20th century witnessed a significant leap forward with the arrival of computers. These powerful machines enabled researchers to perform complex and precise simulations, taking CFD to a whole new level. Today, CFD is a sophisticated field that utilizes:

• Advanced Algorithms: Complex mathematical tools to solve intricate fluid flow problems.
• High-Performance Computing: Powerful computers capable of handling massive datasets and calculations associated with CFD simulations.
• Visualization Tools: Software that translates the data generated by CFD simulations into clear and insightful visuals.

The Pillars of CFD: Governing Equations and Discretization Methods

At the heart of CFD lie the governing equations that describe fluid behavior. These include:

• Continuity Equation: Ensures that mass is conserved within the flowing fluid. No fluid is mysteriously created or destroyed!
• Navier-Stokes Equations: A set of equations that describe the motion of viscous fluids, taking into account factors like viscosity and pressure.
• Energy Equation: Accounts for the conservation of energy within the fluid, considering factors like heat transfer and work done.

But how do we solve these complex equations? This is where discretization methods come in:

• Finite Difference Method (FDM): This method approximates the derivatives in the governing equations by using difference equations, essentially creating a numerical grid and calculating fluid properties at each point.
• Finite Volume Method (FVM): This method focuses on conserving quantities like mass, momentum, and energy within a finite volume of the fluid.
• Finite Element Method (FEM): This method breaks down the problem domain into smaller, simpler elements called finite elements. The governing equations are then solved on each element and the solutions are stitched together to obtain the overall solution.

Taming the Turbulence: How CFD Deals with the Chaotic

Fluid flow isn’t always smooth sailing. Turbulence, characterized by random and chaotic fluctuations, can significantly impact fluid behavior. CFD employs various turbulence modeling techniques to address this challenge:

• Direct Numerical Simulation (DNS): This approach directly resolves all the scales of turbulence in the flow. However, it requires immense computational resources and is often impractical for complex scenarios.
• Large Eddy Simulation (LES): This method simulates the large, energy-containing scales of turbulence explicitly, while modeling the smaller scales using subgrid-scale models. It offers a good balance between accuracy and computational cost.
• Reynolds-Averaged Navier-Stokes (RANS): This widely used method employs time-averaged equations to model the effects of turbulence. While computationally efficient, it can be less accurate for highly unsteady flows.

The Power of CFD: Advantages and Applications

CFD offers a range of advantages that make it an invaluable tool in various engineering disciplines:

• Cost-Effective: It reduces the need for expensive physical prototypes and extensive testing, saving time and resources.
• Detailed Analysis: CFD provides comprehensive insights into fluid behavior that are difficult or impossible to obtain experimentally.
• Flexibility: It allows simulations under a wide range of conditions and scenarios, enabling virtual testing of various design options.
• Optimization: CFD facilitates an iterative design process, where engineers can analyze results and refine their designs for optimal performance.

Challenges and Considerations in CFD

Despite its strengths, CFD also presents some challenges:

• Computational Resources: Complex simulations can demand significant computational power and time, requiring access to powerful computers.
• Accuracy: The accuracy of CFD results relies heavily on the quality of the mathematical models and numerical methods used. Choosing the right approach is crucial.
• Validation: Simulations need to be validated against experimental data or real-world observations to ensure their reliability.

 

Source : https://www.thehindu.com/sci-tech/science/isro-develops-pravaha-software-for-aerodynamic-design-and-analysis/article68246269.ece