800529 Truck Splash and Spray - Some Recent Results David H. Weir SystemsTechnologyJnc. Hawthorne, CA Congress and Exposition Cobo Halt, Detroit February 25-29, 1980 aim- 400 CORSIWONWEALTH DRIVE »ENNSYLVANIA iso Downloaded from SAE International by University of Edinburgh, Monday, August 27, 2018The appearance of the code at the bottom of the first page of this paper indicates SAE's consent that copies of the paper may be made for persona! or interne! use, or for the personal or internal use of specific clients. This consent is given on the con­ dition, however, that the copier pay the stated per article copy fee through the Copyright Clearance Center, Inc., Operations Center, P.O. Box 765, Schenectady, NX 12301, for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does hot extend to other kinds of copying such as copying for genera! distribution, for advertising or promotional purposes, for creating new collective works, or for resale. Papers published prior to 1978 may also be copied at a per paper fee of $2.50 under the above stated conditions. SAE routinely stocks printed papers for a period of three years following date of publication. Direct your orders to SAE Order Department. To obtain quantity reprint rates, permission to reprint a technical paper or per­ mission to use copyrighted SAE publications in other works, contact the SAE Publications Division. ISSN 0148-7191 Copyright© 1980 Society of Automotive Engineers, Inc. Downloaded from SAE International by University of Edinburgh, Monday, August 27, 2018800529 Truck Splash and Spray - Some Recent Results David H. Weir Systems Technology, Inc. Hawthorne, CA DISCUSSION OF THE ISSUES Movement of a truck along the roadway under wet weather conditions can affect and disturb the adjacent motorist in several ways. The air flow around the truck and in the wake can cause force and moment distur­ bances on the car, particularly when the car is close to the truck or when the ambient wind is such that the car is downwind. The splash and spray in the air can obscure or block the driver's vision, and larger drop­ lets striking the windshield can further ob­ struct vision and increase the requirements on the wipers. Spray and related visibility degradation are emphasized in thi^s paper. The other factors are treated in (1) . The phenomena of splash and spray can be described approximately in simple terms. Splash tends to be relatively large droplets which move in ballistic trajectories. Spray is composed of the smaller droplets, which tend to be suspended in the air and move with the air flow. In general, the formation of spray requires a source of water, such as a stream of splash or a wet surface, plus a relatively high velocity flow of air which helps break the droplets down to a very small size. Typically, spray is formed when a stream of water or large droplets strikes a hard or smooth surface, in the presence of a high velocity air flow. Potentially, then, spray can be alleviated by modifying or re­ moving one or more of these three elements: the water, the surface, or the high velocity air. The physics of splash and spray forma­ tion and propagation are discussed in much greater detail in (1) and (3). Operation of the truck is also influ­ enced by its configuration and the ambient wind. A primary factor is the truck drag which has a direct effect on fuel economy, and it can be either increased or decreased by the presence of devices. The various splash and spray devices can also influence the cost of maintenance, and they can compli­ cate line operations, e.g. , due to brake heating, or when there is a need to install and remove chains. These factors are ad­ dressed subsequently. The ideal device or other solution to the problem would be one which reduced splash Numbers In parentheses designate Refer' ences at end of paper. ABSTRACT This paper highligh