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Volume 83 (2021)
- Issue 6 Pages 547-
- Issue 5 Pages 465-
- Issue 4 Pages 385-
- Issue 3 Pages 249-
- Issue 2 Pages 143-
- Issue 1 Pages 3-
Volume 83, Issue 5
Displaying 1-4 of 4 articles from this issue
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─Validation of snow accretion method using snow accretion development conditions by experiment ─Kohei MUROTANI, Koji NAKADE, Yasushi KAMATA2021 Volume 83 Issue 5 Pages 465-487
Published: 2021
Released on J-STAGE: February 16, 2022
JOURNAL FREE ACCESSIn case where a train travels on the snow covered tracks, snow accretes to train bogies and grows up. When the accreted snow drops off the train bogies, it might damage the railway ground facilities along the tracks, the train devices, etc. To establish countermeasures against such snow accretion damage, we have developed a snow accretion analysis method in order to understand the snow accretion process. The “snow accretion analysis method” developed by this research consists of an “airflow calculation”，a “trajectory calculation” and a “snow accretion calculation”．In the snow accretion analysis method, airflow velocity is obtained by the airflow calculation, trajectory of flying snow is calculated by the equation of motion for gravity and drag using the airflow velocity, snow accretion determination for objects is performed by the snow accretion calculation. When a certain amount of snow accretes to the objects, the accretion shape was suitably taken into consideration in the airflow calculation. We calculate again the airflow velocity using the updated accretion shape and the snow accretion growth using the updated airflow velocity. In this research, two kind of validations are performed using a snowfall wind tunnel. First, a snow accretion analysis on a cubic model is performed, and it was confirmed that the snow accretion analysis reproduces the snow accretion experiment with a relative error of 6%. Next, each snow accretion analyses on two railway car-body models are performed, and it was confirmed that the snow accretion distributions were similar with the experiments. As this result, it became possible to consider places and causes where snow accretion occurs for the railway car-body models by the snow accretion analysis.View full abstractDownload PDF (14430K) -
Takafumi FUKUYAMA2021 Volume 83 Issue 5 Pages 489-505
Published: 2021
Released on J-STAGE: February 16, 2022
JOURNAL OPEN ACCESSDownload PDF (4679K) -
Akihiro FUJIMOTO, Katsuhisa KAWASHIMA, Shun WATABE, Haruhiko MURATA2021 Volume 83 Issue 5 Pages 507-522
Published: 2021
Released on J-STAGE: February 16, 2022
JOURNAL OPEN ACCESSTo elucidate the mechanism whereby vehicles become stranded on roads during heavy snowfall, we investigated the conditions of the compacted-snow road surface under a standing vehicle during heavy snowfall and conducted standing vehicle tests, tire spinning tests and vehicle start tests on compacted-snow roads. We found that compacted-snow road surfaces with the formation of pits and with a rough, wavy, irregular profile were generated under the standing vehicle. From the vehicle tests, we found the following. The wheel load of a standing vehicle, the heat transfer from the vehicle and the spinning of the tires at starting promote the melting and compaction of snow. When snow melts and is compacted under the tire, the tire starts to sink into the snow. At the same time, the sliding friction coefficient of the road surface directly under the tire decreases. It was shown that the stranding of vehicles is less likely to occur as the wheel load increases. The mechanism of vehicle stranding is as follows. Heavy snowfall reduces the smoothness of trafficability and increases vehicle standing time and the number of starts. The increases in standing time and number of starts induce the formation of pits and decrease the friction coefficient. They promote tire spinning that further deepens the pits and decreases the sliding friction coefficient. This negative cycle leads to the stranding of vehicles. This paper gives a chart that shows the flow leading to the stranding of vehicles and the flow for avoiding it.View full abstractDownload PDF (5708K) -
Kota OKETANI, Takane MATSUMOTO, Katsuhisa KAWASHIMA2021 Volume 83 Issue 5 Pages 523-532
Published: 2021
Released on J-STAGE: February 16, 2022
JOURNAL OPEN ACCESSThe mass release of intercepted snow on the lower part of the canopy of an Abies mariesii forest in a mountainous area of Fukushima Prefecture, Japan, was measured using time-lapse cameras to clarify the relationships between the occurrence of snow mass release and meteorological conditions. Based on the number of occurrences in a 1-h shooting interval, mass release events can be classified into the following two types: Type I events, in which a limited number of mass releases are recognized, and Type II events, in which mass releases are recognized at many branches during a shooting interval. Moreover, Type II events can be classified into two types: Type II-A, in which most of the intercepted snow masses on many branches are released rapidly and disappear in several hours, and Type II-B, in which snow masses on many branches continue to be released gradually for several days. A comparison with the meteorological conditions at a weather station near the observation site during each type of mass release event revealed that Types I, II-B, and II-A occur mostly when air temperature is lower than 0℃, between 0 and 2℃, and higher than 2℃, respectively. In contrast, no significant differences of mass release event type were associated with differences in wind speed or global radiation. These results indicate that mass release of intercepted snow on the lower part of the canopy is controlled mainly by air temperature.View full abstractDownload PDF (4169K)
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