# NTNUJAVA Virtual Physics LaboratoryEnjoy the fun of physics with simulations! Backup site http://enjoy.phy.ntnu.edu.tw/ntnujava/

## Information about this web site => Request for physics Simulations => Topic started by: Fu-Kwun Hwang on June 17, 2009, 10:12:40 am

 Title: torsional wave Post by: Fu-Kwun Hwang on June 17, 2009, 10:12:40 am The fllowing simulation was created due to the following request:QuoteHello Fu- Kwun Hwang I would like to introduce myself; I am a metalwork sculptor living in Sheffield, England and came across your wonderful animated pendulum simulations on the COLOS website while researching a current project. This project involves the creation of a kinetic artwork based on a human powered 'wave" intended to mimic the effect of  the 'Mexican waves'  seen in sports stadiums around the world. After seeing your computer simulations I would be very interested in talking to you about your work and hope you could help me with the mathematics of achieving the effect I am trying to create.   My own background is as an artist and metalworker and although I do not have a science back ground I enjoy the application of science in my art.  I have made  a 1:20 Scale model and achieved the 'Wave' effect I wanted with the model suspended in air. To progress things further I am trying to find somebody who can help me with the mathematics so i can produce working drawings and create kinetic artwork for a freshwater pool in a Lancashire quarry in the UK; (For further information - see attached file - echofly 2.pdf )I understand this may not be your normal line of work, but if it is of interest?; I can send you more information and I would welcome an opportunity to discuss it with you in more detail. Kind regards Robin Dobson-*-The angle for each one is $c_i$, which is a function of time t. The restore torque is assume to be $k*(c_{i+1}-c_i)-k*(c_i-c_{i-1})=k*(c_{i+1}+c_{i-1}-2*c_i)$,The torque due to gravitation force is $m*g*h*\sin(c_i)/I$, where  $I$ is the moment of rotational inertia.A damping torque $-b*\omega_i$ is also added, where $\omega_i=\frac{d c_i}{dt}$ Title: New version of torsional wave Post by: Fu-Kwun Hwang on April 16, 2010, 11:03:07 am Here is another version of torsional wave (demostration)Change the c angle with slider and watch how wave propagate.The slider for i can be used to change angle for i-th element.The force acting on each element is$F_i= K* c_i + K_ij * (c_{i+1}-c_i)+K_ij (c_i-c_{i-1})-b*\omega_i$where $c_i$ is the i-th angle, $\omega_i$ is the angular velocity, $b$ is damping constant, $K_ij$ represent interaction between elements.