From 4344a732318d953c08e406d30bf1205a73af7a7c Mon Sep 17 00:00:00 2001
From: Henry Weller <http://cfd.direct>
Date: Sun, 3 Apr 2016 22:17:10 +0100
Subject: [PATCH] applications/test/rigidBodyDynamics/pendulum: Very simple
test/demonstration of the rigidBodyDynamics library
Simple swinging pendulum simulation with 1-DoF. The motion is integrated
using a symplectic method for just over 2-periods.
---
.../rigidBodyDynamics/pendulum/Make/files | 3 +
.../rigidBodyDynamics/pendulum/Make/options | 5 +
.../rigidBodyDynamics/pendulum/pendulum.C | 98 +++++++++++++++++++
3 files changed, 106 insertions(+)
create mode 100644 applications/test/rigidBodyDynamics/pendulum/Make/files
create mode 100644 applications/test/rigidBodyDynamics/pendulum/Make/options
create mode 100644 applications/test/rigidBodyDynamics/pendulum/pendulum.C
diff --git a/applications/test/rigidBodyDynamics/pendulum/Make/files b/applications/test/rigidBodyDynamics/pendulum/Make/files
new file mode 100644
index 00000000000..f860e98af44
--- /dev/null
+++ b/applications/test/rigidBodyDynamics/pendulum/Make/files
@@ -0,0 +1,3 @@
+pendulum.C
+
+EXE = $(FOAM_USER_APPBIN)/pendulum
diff --git a/applications/test/rigidBodyDynamics/pendulum/Make/options b/applications/test/rigidBodyDynamics/pendulum/Make/options
new file mode 100644
index 00000000000..4a9d828b67c
--- /dev/null
+++ b/applications/test/rigidBodyDynamics/pendulum/Make/options
@@ -0,0 +1,5 @@
+EXE_INC = \
+ -I$(LIB_SRC)/rigidBodyDynamics/lnInclude
+
+EXE_LIBS = \
+ -lrigidBodyDynamics
diff --git a/applications/test/rigidBodyDynamics/pendulum/pendulum.C b/applications/test/rigidBodyDynamics/pendulum/pendulum.C
new file mode 100644
index 00000000000..23c35c4af34
--- /dev/null
+++ b/applications/test/rigidBodyDynamics/pendulum/pendulum.C
@@ -0,0 +1,98 @@
+/*---------------------------------------------------------------------------*\
+ ========= |
+ \\ / F ield | OpenFOAM: The Open Source CFD Toolbox
+ \\ / O peration |
+ \\ / A nd | Copyright (C) 2016 OpenFOAM Foundation
+ \\/ M anipulation |
+-------------------------------------------------------------------------------
+License
+ This file is part of OpenFOAM.
+
+ OpenFOAM is free software: you can redistribute it and/or modify it
+ under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+ ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with OpenFOAM. If not, see <http://www.gnu.org/licenses/>.
+
+Application
+ pendulum
+
+Description
+ Simple swinging pendulum simulation with 1-DoF. The motion is integrated
+ using a symplectic method for just over 2-periods.
+
+\*---------------------------------------------------------------------------*/
+
+#include "rigidBodyModel.H"
+#include "joints.H"
+
+using namespace Foam;
+using namespace RBD;
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+int main(int argc, char *argv[])
+{
+ // Create a model for the pendulum
+ rigidBodyModel pendulum;
+
+ // Join a weight to the origin with a centre of mass -1m below the origin
+ // by a hinge which rotates about the z-axis
+ pendulum.join
+ (
+ 0,
+ Xt(vector(0, 0, 0)),
+ joint::New(new joints::Rz(pendulum)),
+ rigidBody::New("hinge", 1, vector(0, -1, 0), 0.02*I)
+ );
+
+ // Create the joint-space state fields
+ scalarField q(pendulum.nDoF(), Zero);
+ scalarField w(pendulum.nw(), Zero);
+ scalarField qdot(pendulum.nDoF(), Zero);
+ scalarField qddot(pendulum.nDoF(), Zero);
+ scalarField tau(pendulum.nDoF(), Zero);
+
+ // Set the angle of the pendulum to 0.3rad
+ q[0] = 0.3;
+
+ // Set the gravitational acceleration
+ pendulum.g() = vector(0, -9.81, 0);
+
+ // Integrate the motion of the pendulum for 4.1s (~2-periods) using a
+ // symplectic method
+ scalar deltaT = 0.01;
+ for (scalar t=0; t<4.1; t+=deltaT)
+ {
+ qdot += 0.5*deltaT*qddot;
+ q += deltaT*qdot;
+
+ pendulum.forwardDynamics
+ (
+ q,
+ w,
+ qdot,
+ tau,
+ Field<spatialVector>(),
+ qddot
+ );
+
+ qdot += 0.5*deltaT*qddot;
+
+ Info<< "Time << " << t << "s, angle = " << q[0] << "rad" << endl;
+ }
+
+ Info<< "\nEnd\n" << endl;
+
+ return 0;
+}
+
+
+// ************************************************************************* //
--
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