Guidance to Predict and Mitigate Dynamic Hydroplaning on Roadways (2021) / Chapter Skim
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Pages 70-82
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71 3. Step 3: Select the design speed and braking deceleration, design vehicle, and tire condition (or approve the default)
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72 However, it is recommended that a relatively coarse resolution in the horizontal dimensions (e.g., about 2-12 ft) be used to speed up the processing.
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73 4.2.2. Calculate the WFT Using a Modified Gallaway Equation The WFT is calculated for each streamline using a modified version of the Gallaway equation for 1-D flow.
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From page 74... ...
74 segment i of the streamline can therefore be calculated knowing the WFT at the end of segment i1 with the WFT at the end of the first segment calculated using the 1-D Gallaway equation. It might seem reasonable to assume that WFTi-1+ = WFTi-1; however, because of the change in slope between the two segments, the WFT at the beginning of segment i will be slightly different than the WFT at the end of segment i−1.
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From page 75... ...
75 The second issue related to the 1-D aspect of the streamlines is that the flow is restricted to follow the road geometry. In regions where the geometry changes, adjacent streamlines can have different lengths, resulting in very different WFTs.
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76 and two water temperatures of 25 °C (77 °F)
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77 The neighborhood size has to be large enough that it includes at least one cell with calculated WFT not equal to zero and representative of that cell (i.e., has a long streamline crossing the neighborhood)
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78 (a) Neighborhood size = 1 cell, bandwidth = ω/15, max WFT = 3.1 mm (b)
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From page 79... ...
79 (a) Bandwidth = ω/15, max WFT = 3.5 mm (b)
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80 4.3. PERFORMANCE MARGIN ESTIMATION Once the Hydroplaning Potential Assessment Tool has estimated the maximum WFT, the user can confirm the defaults or enter the vehicle characteristics and operating conditions that would be used for the analysis.
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81 (a) 2 lanes, Sx = 1%, v = 136 km/h, WFT = 1.9 mm, PM = 0.112 (b)
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From page 82... ...
82 - Given the budget available for the project, only very limited additional field testing was conducted as part of the effort, and the majority of the verification and validation was based on results from previous research found in the literature. • Additional simplifications were needed to be able to run the practical hydroplaning risk Assessment Tool without the need to purchase licenses for simulation software and preparing complicated input files.
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