Tech Briefs

FSI Analysis of Wood Type Golf Clubs with Air Guides

A wood type golf club, often called “wood club” or simply “wood”, is a long slender golf club with a large, rounded head (see Figures 1 and 2; today, the head of a wood club is not necessarily made of wood). It is typically used for long distance shots.

Figure 1  Wood club (left); taking a shot with a wood club (right)

When the golfer takes a full swing, the head of a wood type club can reach a speed of more than 100 miles per hour. At these speeds, the aerodynamic force acting on the club can have a significant effect on the position of the club head. As seen in Figure 2, when the head is about to hit the golf ball, the air pressure acts on the hitting surface with its designed angle (loft angle), which will create a downward force pushing the head down. This force depends on the speed of the club head: the faster the club head travels, the bigger the force. This force makes it harder to master the use of a wood club.

Figure 2  Loft angle of golf club head

In an innovative wood club design, air guides are attached to the club head to give the golfer better control. The air guides are designed to reduce the downward deflection caused by the aerodynamic force (see Figure 3). In this Tech Brief, we demonstrate how engineers use ADINA to study the effect of the air guides.

Figure 3  Typical wood club and a club head with air guide (US Patent No. 7390266)

Figure 4 shows part of the fluid mesh of the 3D ADINA FSI model. To simplify the model, the grip end is attached to a spring in order to simulate the golfer’s wrists (the arms here are considered to be rigid and therefore not included in the model). The stiffness of the spring is determined by experimental data. In the steady-state FSI analysis, the swing of the club from left to right is represented by the prescribed flow of fluid (air) traveling in the opposite direction, i.e., from right to left. At the start of the simulation, the club is at the position desired by the golfer; during the course of the analysis, the air pushes the head to the left and down.

Figure 4  Detail of fluid mesh (on a cutting plane through the club head)
used in FSI model of the wood club with air guide

Some simulation results are shown in Figures 5 and 6. Table 1 gives the deflection of the head with and without the air guide for various swing speeds.

The movie above shows the relative movement of the head from its desired position, caused by the aerodynamic force. The velocity vector field is consistent with the relative velocity of the head as it reaches a speed of 100 mph. The air guide virtually eliminates the downward movement, so we can only see the head move to the left.

Figure 5  Velocity vector plot around head on a cutting plane for club without air guide
at a swing speed of 100 mph (units used: mm, sec)

Figure 6  Velocity vector plot around head on a cutting plane for club with air guide
at a swing speed of 100 mph (units used: mm, sec)

Table 1  Deflection of a wood club head during various swing speeds

 Velocity(mph) Deflection (mm) - no air guide Deflection (mm) - with air guide 70 -7.307 2.578 80 -9.557 3.152 90 -12.10 3.727 100 -14.96 4.335

From the above results, one can clearly see the reduction of deflection by the air guide. Using ADINA, the engineers obtained detailed insights for the air guide performance. Such insights were very helpful for later design improvements.