When an object moves through water, it displaces the water molecules in its path, causing a disturbance in the water. This disturbance propagates outward from the object in the form of waves. The circular waves that form around the object are known as "circular or ripple waves" or sometimes referred to as "circular wave patterns."
These circular waves occur due to the principle of wave interference. As the disturbance spreads outwards, it creates a series of expanding concentric circles. Each circle represents a wavefront, which is a line connecting points of equal disturbance or phase. These wavefronts propagate away from the object at a constant speed.
The circular shape of the waves is a result of the waves spreading out uniformly in all directions from the source of disturbance, which is the moving object. The waves appear as concentric circles because the disturbance created by the object spreads equally in all directions, causing the wavefronts to be circular.
It's important to note that these circular waves are a simplified representation of the actual wave pattern. In reality, the waves can be more complex, and their behavior depends on various factors such as the speed and shape of the object, the depth of the water, and the viscosity of the fluid. However, for a basic understanding, circular waves are a useful concept to explain the phenomenon.