When ever a body is moving in a circular there is a force created known as centripetel force(also known as centre seeking force) which tends to bring the body to its centre.the body does not goes to the centre because there is an another force acting opposite to the direction of the crntripetel force and balances it.but it is not the reaction force.and the centripetel acceleration is the increase _of the centripetel force at a fixed rate in other words the velocity or the angular velocity increases at a fixed rate.and hence, the angular velocity will increase and so the force will also increase.
the formula for calculating the centripetel acceleration is
a=v sq./r. where r is the radius.