This project is a C++ tool to calculate the optimal velocity at which bodies should move through rain to minimize wetness. The program able to estimate how wet a body gets when it travels a straight path under rain at a fixed velocity. It finds a velocity near the minimum using Brent's method and performs a parabolic fit around this point to better estimate the minimum. Bodies are defined in XML files, and simulations are configured through an Input.xml file.

Requirements:

• clang++ (C++17 or newer)
• make

From the Code directory build with:

make

Other useful commands:

make debug   # build with debugging flags
make format  # format source files with clang-format
make clean   # remove object files and executable

The compiled binary is main.exe.

The program requires:

• An Input.xml file in the same directory as main.exe and the Makefile, which specifies the simulation settings (see Input.xml for an example).
• A body XML file which describes the body shape and dynamics (see the Bodies folder for examples).

Run with:

make run

Or directly:

./main.exe   # Linux/macOS
.\main.exe   # Windows

Renderings of the bodies defined in WalkingMan.xml and RunningMan.xml respectively.

Below is an example output:

############################################################################################################
# Minimums of wetness found for the following parameters:
# Body = RunningMan.xml, vmax = 2 vfall
# dx = 0.01 m, nstep = 50
# nfit = 9, dv = 0.006 vfall
# Columns:
# vcross (vfall)   vtail (vfall)   vopt (vfall)   vopt_std (vfall)   Rmin (m^2)   Rmin_std (m^2)
############################################################################################################
0.000000000000	0.000000000000	2.000000000000	0.000000000000	0.438482950029	0.000000000000
0.000000000000	0.500000000000	0.874593172486	0.000800133595	0.268469915778	0.000006118143
0.000000000000	1.000000000000	1.201341426966	0.000861805107	0.163199562816	0.000020078286
0.500000000000	0.000000000000	2.000000000000	0.000000000000	0.458102375515	0.000000000000
0.500000000000	0.500000000000	1.123105402195	0.001327244707	0.333991782935	0.000008355485
0.500000000000	1.000000000000	1.267568725214	0.000436180555	0.216661264164	0.000005192611

Running the program without changing Input.xml should yeld this same output. Note that all velocities are expressed in units of the vertical velocity of the rain vfall, and that Rmin represents the minimum wetness achieved at the optimal velocity vopt.