Effect Of Aerodynamic Drag Force On Trailers

Heavy vehicles undergo the effect of aerodynamic drag force that carries large trailers with variable container shapes and loads. This effect of aerodynamic drag is mandatory as many vehicles use different containers for the transport of goods that are variable in load and vary in the shape of the container. The fuel consumption of these vehicles is very high and thus results in spending a large amount of money annually. The aerodynamic drag force is in the best interest as it makes most of the fuel consumption. To overcome this problem an analysis of the aerodynamic design can be performed for further design modifications when required.

To make this research, databases like Scopus, google scholar, and web of science has been used as the source for the background work. These sources contribute information in the chosen field by supplying research papers related to the topic. Scopus provides a lot of research information in the related field, but it is problematic for filtering the search as the page must be refreshed every time the search has been refined. The method of refining the searches is well, but the citations must be downloaded. The web of science has a user-friendly interface that enables all the researchers to approach the respective field of information. Web of science has similar methods for refining your searches but has an advantage of multiple search fields and gather the desired information. It provides another search tool to refine your search on the same page without the necessity to go through all the information provided. Among the three the google scholar is more user-friendly to use and is more illuminative. It provides the ease of refining your searches and filter them to limit your search relative to your field of research. It provides a huge amount of information related to the field of research by adding journals, articles, research papers, and magazines. Google Scholar lets you store the information online for referencing in the future. It provides the citations readily in the database search field with 5 different formats without the need of downloading the citations and gives you topic related articles under every article. It also has a special tool that can allow you with different types of formats that are available like word, pdf, or read-only. Google Scholar allows you to go through information by letting you know how many researchers have cited that data so that you can go over that data. Among the other databases, I chose to go through google scholar as it has many advantages when compared to the other two databases.

As the google scholar as my database, I have performed my research in the field of my research topic ‘aerodynamic drag force’. Google scholar enabled me to go through a lot of research papers and articles. These research papers, articles, and journals have a lot of information regarding my field of research and helped me gather a lot of information that assists my research. Initially, a search for the basic concept in the required field was performed for better understanding in the area of research by going through the previously published research papers. Now, by limiting the search related to the topic and by the year of publication of the research papers or articles on aerodynamic drag force on vehicles with trailers. This led to many papers and journals based on the aerodynamic drag, but most of the research papers were about the improvisation of the fuel efficiency of heavy vehicles and aerodynamic effect on heavy vehicles. Going through these papers gave five research papers that can lead to research in the field of the research.

Thoroughly following the methodology and analyzing the acquired research papers that are related to the research topic. The first research paper written by Surcel M.D and Shetty M. is “Evaluation of the influence of stakes on drag and fuel consumption for a tractor logging trailer combination”. The paper explains the CFD analysis and wind tunnel testing for the inspection and advancement of aerodynamic design for the trailers for future applications [1]. An experiment was conducted involving closed-loop wind tunnel testing as per SAEJ1252 standard [1]. With standard parameters and at a speed of 102km/hr and a temperature of 22.7°C, Reynolds number with a value of 1.8*105 was attained. At different yaw angles, a CFD analysis was carried out involving mesh sensitivity for accurate results. The analysis was carried out involving mesh sensitivity is because of the variation involved by the direction and speed of the wind. With real-world conditions and standard parameters, a grid model is achieved with accurate results [1]. A comparison between two conditions was carried out with and without stakes. The comparison resulted closely to the CFD analysis and practical result that there is a decrease in drag force without stakes [1]. Along with the drag force test, a fuel consumption test was also carried out for the advancement in the research. The outcome of the results shows that there is a reduction in the drag force about 27.61%±7.65%. The test on the fuel consumption results that when the vehicle travels without stakes the fuel can be saved up to 14.59%±2.43% [1]. The analysis was carried out with all the major conditions including wind speeds and fuel consumption but did not consider the cooling and radiator system in the analysis. The design of the trailer can be optimized by tweaking the aerodynamic design of the trailer for more economical results.

The second paper provides more information about the drag by using case studies on drag analysis of tractor-trailer with trailer combinations. The paper is about the influence of trailer combinations of a tractor on aerodynamic drag. The paper uses containers with rectangular shape load on the trailer. A CFD analysis is conducted on different trailer combinations [2]. The drag coefficient of the trailer is measured [2]. To understand the possible reason for the contribution of drag, analysis is performed at various yaw angles and speeds. The drag coefficient was more sensitive at the 0-5° yaw angle for the long trailer combination. The analysis also resulted that the drag was low for the center axle trailer and high for the rigid truck trailer. The paper also tells about the gap between the trailer and the prime mover and how it effects the aero drag [2]. The smaller the gap the lower the drag force and higher stability of the vehicle. the increase in the gap reduces the stability of the vehicle due to the increase in the drag force. The difference in the gap between the vehicle and trailer is directly proportional to the effect of the drag force [2]. The drag force is also linear to the effect of fuel consumption, as there is an increase in the drag force the fuel consumption also increases accordingly.

The third research paper by Richard M. Wood is mainly concentrated on the technicality of the drag distribution involved between trailer and tractor. This paper indicates the placement of the drag force and its deflection [3]. Some experiments and analyses were conducted on the drag force relative to the change in the design or modification of the design of the tractor and trailer. The main aim of the experiment was to reduce the drag force by tweaking the design of a standard trailer and addons were introduced for introducing features and experience the drag between the gaps [3]. The new features were introduced by following the standard safety measures, cost, breaking, wear and tear of tires, stability, handling, and other geometries that the function of the tractor-trailer does not get interrupted. A base device is added for the trailer to eliminate the wind flow at the two axles which help in decreasing the unsteady flow of winds which destabilize the tractor, for appropriate flow characteristics a rotatable gear is used to guide the winds [3]. A vortex trap was developed to eliminate the crosswinds that communicate low pressure at the front surface. The base vortex flow device extends the flow and increases the vortex flow to the base to reduce the drag and stable the base wake flow which has the high-pressure condition. A base extension add-on which is fixed at the back end to enhance the steady flow and diminish the drag force by 25% and elevates the fuel-saving by 10% at a speed of 65mph.

The last paper discusses the skirting provided at the side with little modifications. Side skirts give the advantage of controlling the wind flow under the trailer at the wheelbase and the axle. This paper is written about the effect of drag on the structure and wheels where there is an underbody drag force involved which plays a major role in the aerodynamic design. These skirts are analyzed under CFD and wind tunnel tests [4]. A simulation is also performed known as eddy current simulation and estimation was found out to be as close to the previous results [4]. At 45° as the flap angle, the drag is high and at 60° as the angle, the effect of reducing the drag was highest.

Hence, the research on the effect of aerodynamic drag force on trailers can explain the effect of drag force can be reduced by tweaking the design of the trailers and installing new features which can diminish the effect of drag. Some areas or gaps are not considered and are neglected which can lead to the effect of drag.

References

1. Shetty, M. and Surcel, M.D., 2014. Evaluation of the Influence of Stakes on Drag and Fuel Consumption for a Tractor-Logging Trailer Combination. SAE International Journal of Commercial Vehicles, 7(2014-01-2447), pp.653-665.
2. Martini, H., Bergqvist, B., Hjelm, L. and Löfdahl, L., 2011. Influence of Different Truck and Trailer Combinations on the Aerodynamic Drag (No. 2011-01-0179). SAE Technical Paper.
3. Wood, R.M., 2008. Operationally-Practical & Aerodynamically-Robust Heavy Truck Trailer Drag Reduction Technology. SAE International Journal of Commercial Vehicles, 1(2008-01-2603), pp.237-247.
4. Hwang, B.G., Lee, S., Lee, E.J., Kim, J.J., Kim, M., You, D. and Lee, S.J., 2016. Reduction of drag in heavy vehicles with two different types of advanced side skirts. Journal of Wind Engineering and Industrial Aerodynamics, 155, pp.36-46.