IMPACT OF JET 1

Impact of Jet

Discussion

These data results indicate that the rate of delivery of momentum varied from one type of vane to another and depended on some factors. These included the time over which the water was made to flow; the mass of water; and the velocity at which it was flowing. The momentum impact on the hemi vanes generated the highest amount of experimental force. This observation can be attributed to the fact that they were aligned at 1800 and hence the water could strike their surfaces without much interference (Falkovich, 2011). For the same volume of water and nearly equal amounts of time, conical vanes produced more force than the flat ones. This is also an effect of their 120-degree alignment which offers lower resistance to the flow of water compared to the 90 degrees in the flat ones. This leads to the conclusion that the impact of a water jet on hemi vanes yields the greatest force followed by that on the conical and finally flat vanes. This knowledge is the basis upon which components such as pump impellers are designed so as to produce designs that would yield the greatest momentum force and hence push water at great velocities towards their destination.

For all the different types of vanes, one common thing was observed: The velocity from the jet was less than the exit velocity after reaching the vanes. This can be attributed to a number of factors. One of these is loss of kinetic energy as the water moves along the jet. This is because the surfaces over which it moves are not smooth and the frictional forces lead to a loss in energy. It is also due to turbulence when water finally hits the vanes. It requires a great amount of energy to form the eddies generated at the vanes and hence this energy is extracted from the water. The resulting loss in kinetic energy leads to a lower exit velocity. Another factor that has contributed to this phenomenon is the increase in pressure as the water flows towards the vanes. When leaving the vanes, the water is at a low pressure and hence low velocity. When approaching the vanes, however, the velocity is reduced by the increase in pressure.

The theoretical (Ft) and Experimental (Fe) forces were observed to compare differently from one type of vane to another also. Generally however, the experimental ones were lower than the theoretical ones. This can be due to multiple factors but is majorly a result of the errors during the experiment. The difference was greatest in the flat vanes where the theoretical values were significantly higher than the experimental ones. This shows that they are the least efficient. On the other hand, the hemi vanes were the most efficient as the forces were not extremely different.

The values for the experimental forces also show that they had a sharp rise for a brief moment at the beginning of each test. After this, they leveled off and acquired a gradient that was almost similar to that of the graphs for the theoretical forces (Falkovich, 2011). This sharp rise may have been due to the initial fast jets that created an impulse in the stationary vanes and eventually leveled as the vanes attained a uniform velocity. This shows that the forces exerted by a momentum flow vary with its rate of flow.

Errors in the lab

Like in any other type of experiment, errors might have occurred when undertaking this one and therefore leading to inaccurate results. Some of these are mentioned here. Firstly, the adjusting nuts on the impact of jet measuring device might have been turned improperly. This is because when turning them, the level should not reach such a point where it is in line with the top plate. Such an error might have occurred and hence the readings made at the said points might have been inaccurate.

Another common error that might have occurred in this experiment was incorrect reading of time. The flow rate was largely determined by the quantity of water being supplied alongside the duration it would hit against the plates. If the timer is started when the beam has moved to the horizontal position again, the readings made are inaccurate. Since the time is used to calculate the flow rate, then the error is not only transferred but also magnified when doing the computations. This makes the entire data set inaccurate.

Thirdly, there might have been errors which occurred when making the computations themselves. This is due to the fact that the data contained some extensive decimals and hence it became necessary to truncate or round them off. When doing so, some inaccuracies might have been introduced since values that have been truncated or rounded up/down are not as accurate as the original set of data. When used in producing the necessary graphs for further analysis, such values might not yield curves that represent the true picture of the scenario.

References

Falkovich, G. (2011). Fluid Mechanics, a short course for physicists. Cambridge University