[mod] readme

README.md

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+# Simple IBM Solver
+
+[![License](https://img.shields.io/github/license/NaokiHori/SimpleIBMSolver)](https://opensource.org/licenses/MIT)
+[![Last Commit](https://img.shields.io/github/last-commit/NaokiHori/SimpleIBMSolver/main)](https://github.com/NaokiHori/SimpleIBMSolver/commits/main)
+
+[![Simulation Snapshot](https://github.com/NaokiHori/SimpleIBMSolver/blob/main/docs/source/snapshot2d.png)](https://youtu.be/nMAyrIYET10)
+
+## Overview
+
+This library numerically simulates the motion of rigid particles in two- and three-dimensional Cartesian domains using the finite-difference and immersed boundary methods.
+
+## Dependency
+
+This solver is built on top of [`SimpleNSSolver`](https://github.com/NaokiHori/SimpleNSSolver). 
+Please check its repository for dependency details.
+
+## Quick Start
+
+1. **Set up your workspace**
+
+   ```console
+   mkdir -p /path/to/your/directory
+   cd /path/to/your/directory
+   ```
+
+2. **Clone the repository**
+
+   ```console
+   git clone --recurse-submodules https://github.com/NaokiHori/SimpleIBMSolver
+   cd SimpleIBMSolver
+   ```
+
+3. **Set the initial condition**
+
+   Python 3 is used to conveniently initialize the flow fields. 
+   Alternatively, `NPY` files can be provided in a different manner under `initial_condition/output/`.
+
+   ```console
+   cd initial_condition
+   make output
+   bash exec.sh
+   cd ..
+   ```
+
+4. **Build the solver**
+
+   ```console
+   make output
+   make all
+   ```
+
+5. **Run the simulation**
+
+   ```console
+   bash exec.sh
+   ```
+
+## Note
+
+The immersed boundary method and the collision model are based on [this publication](https://www.sciencedirect.com/science/article/pii/S0045793021003716) with some modifications.
+