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# Free Example of Latent Speed Essay

Driving in the rain can be an exhilarating experience, and is a passion for many. However, driving through freezing rain can pose many hazards that one would do well to be aware of. One of the more serious problems is the frosting or freezing-up of the windshield, which affects visibility and thereby driver performance. This paper will explore possible solutions that will enable the driver to optimize the vehicle’s speed and, along with other controlling factors such as using the defroster at a particular temperature, using the intermittent setting on the windshield wipers and other methods at his or her disposal, have the windshield free of frost while achieving the minimum possible travel time from point A to point B. The solutions will range from the simple, such as controlling internal vehicular temperature, to the complex, such as using Computational Fluid Dynamics vis-à-vis the Navier-Stokes Equations in their simpler forms as potential flow equations, to achieve the desired solution. Certain assumptions will be made regarding the boundary layer, wind speed relative to zero vehicular speed, and wind direction, in order to present a more plausible solution than if these aspects were factored in. In conclusion, the best options will be discussed with regards to convenience, practicality and real-world applicability.

Latent Speed

Driving through the freezing rain is not the easiest of tasks. It takes a cautious and experienced driver to negotiate even the safest of roads under such conditions, and as such it is to be avoided at all costs – “freezing rain and driving don’t mix” (MacEn, 2007). ^{[1]} The phenomenon of frosting further exacerbates the problem, leaving the driver will little choice but to either slow down his speed to a crawl, or make frequent stops to de-ice the windshield. This paper will explore possible solutions, and propose some which will let the driver travel at the maximum speed possible without having to worry about windshield frost, and thereby, visibility. Attention will be given to the fact that the solution(s) proposed will be practical to apply, and easy to implement. There is at least one known patent application covering this purpose ^{[2]}, and it will be discussed briefly. The bulk of the solutions, however, will not involve the addition of technology or manual methods of defrosting, as this may be impracticable.

Frost is primarily caused by the super-saturation of water over a cold surface that is unable to facilitate evaporation at a similar level to that of condensation. ^{ }Therefore, condensation happens faster than evaporation (Craigen, D, 2003). Because the windshield is made of glass, an ineffective conductor of heat, conditions are ideal for frost formation. This phenomenon is what causes decreased visibility because although water is transparent, frost is not. This brings us to the next problem of removing the frost. ^{[3]}

Frost on a stationary vehicle can either be removed by physically scrapping it off with a de-icer, or heating the surface of the windshield with a hot blower. This will increase the temperature on the surface of the glass, thereby increasing the evaporation rate and dispelling the frost. ^{[3] }In a moving car, this is obviously not possible. Which means other methods should be sought out to achieve the objective.

A very simple solution is to coat the windshield with an anti-freeze. This will allow your windshield to maintain clarity despite the rainfall. It works by not allowing the rain to clog up the minute pores on the windshield surface, forcing it to roll off much quicker instead. Most glass treatment liquids act in much the same way, and are effective methods of retaining good visibility even in adverse conditions. More relevant to this paper, the rapid removal of water slows down the condensation process and brings it closer to the natural evaporation process, limiting or controlling frosting. This will allow the driver to travel at high speeds without losing visibility or driving. Depending on the road and the type of tires used, the car can travel at or near the speed limit, which is typically 65 miles per hour. ^{[4]}

When using a defroster at the highest setting, the optimum speed to maintain the defrosting effect will need to be calculated using simplified Navier-Stokes equations which eliminate viscosity and vorticity to give full potential equations, which can further be simplified to yield linearized potential equations. Used along with Heat Equations, the exact speed at which the temperature differential between the inner and outer surfaces of the windshield are maintained at an equilibrium that prevents the formation of frost can be calculated. ^{[5]}Assuming an external wind speed of zero relative to the speed of the vehicle, the velocity factor V will be the value of the solution. This velocity V can be further optimized by the assumption that the car’s defroster is turn on to the maximum setting, and the option for recirculation of air is off. Turning off the recirculation option ensures that the temperature differential of the inner and outer surfaces of the windshield is kept to a minimum. However, it must be stated here that fuel consumption will show a marginal increase of about 8 to 10%. ^{[6]}

In order to compute this problem using CFD approach and relevant technology such as computational aerodynamics, the information about boundary layer conditions, the geometry of the problem analysis surface, and prevailing temperature conditions inside and outside the car need to be defined. Once this information is fed, heat equations once again need to be employed. As adjustments are made, the exact surface velocity of the wind at the point when the temperature differential between the internal and external surfaces of the windshield is sufficient to maintain thaw will be our resultant solution, i.e. the optimal speed of the car to prevent windshield frost. However, CFD technology is not known for its accuracy, and at best, will be an approximation.

Results

In order to ascertain the best option for our objective of identifying the optimum speed for a car traveling in freezing rain to avoid frosting on the windshield, we essentially used two methods: one being the use of an antifreeze applied to the windshield prior to driving, and the other being a combination of calculations and CFD modeling to ascertain the impact of a defroster in helping maintain thaw. The calculations require several variables to be defined in order to correctly give the optimal speed. However, if a number of assumptions are made about the fluid and its behavior, the results are much easier to obtain.

Conclusions

Two ideal scenarios are now made apparent: the use of antifreeze on the windshield, and the use of a defroster on maximum setting without air recirculation. A further inference about the usage of power to operate the defroster can be made. If increased fuel consumption is considered an undesirable side effect, then using antifreeze will be the only choice left. The cost of antifreeze per application and per trip will be considerably less than the increased cost of fuel per trip, and therefore the only practicable solution.