{"@context":{"@vocab":"https://cir.nii.ac.jp/schema/1.0/","rdfs":"http://www.w3.org/2000/01/rdf-schema#","dc":"http://purl.org/dc/elements/1.1/","dcterms":"http://purl.org/dc/terms/","foaf":"http://xmlns.com/foaf/0.1/","prism":"http://prismstandard.org/namespaces/basic/2.0/","cinii":"http://ci.nii.ac.jp/ns/1.0/","datacite":"https://schema.datacite.org/meta/kernel-4/","ndl":"http://ndl.go.jp/dcndl/terms/","jpcoar":"https://github.com/JPCOAR/schema/blob/master/2.0/"},"@id":"https://cir.nii.ac.jp/crid/1362825895629677440.json","@type":"Article","productIdentifier":[{"identifier":{"@type":"DOI","@value":"10.1017/s0022112000001014"}},{"identifier":{"@type":"URI","@value":"https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022112000001014"}},{"identifier":{"@type":"NAID","@value":"30022892010"}}],"dc:title":[{"@value":"Saltation and incipient suspension above a flat particle bed below a turbulent boundary layer"}],"description":[{"type":"abstract","notation":[{"@value":"<jats:p>Experiments were conducted in a wind tunnel in which a turbulent boundary layer \nwas naturally grown over flat beds of three types of nearly mono-disperse spherical \nparticles with different diameters, densities and coefficient of restitution (<jats:italic>r</jats:italic>) (snow, \n0.48 mm, 910 kg m<jats:sup>−3</jats:sup>; mustard seeds, 1.82 mm, 1670 kg m<jats:sup>−3</jats:sup>, \n<jats:italic>r</jats:italic> = 0.7; ice particles, 2.80 mm, 910 kg m<jats:sup>−3</jats:sup>, <jats:italic>r</jats:italic> = 0.8–0.9). \nThe surface wind speeds (defined by the friction \nvelocity <jats:italic>u</jats:italic>∗) were varied between 1.0 and 1.9 times the threshold surface wind speed \n(defined by <jats:italic>u</jats:italic>∗<jats:sub><jats:italic>t</jats:italic></jats:sub>). The trajectories, and ejection and impact velocities of the particles \nwere recorded and analysed, even those that were raised only about one diameter into the flow.</jats:p><jats:p>Measurements of the average horizontal flux of saltating particles per unit area, <jats:italic>f</jats:italic>(<jats:italic>z</jats:italic>), \nat each level <jats:italic>z</jats:italic> above the surface showed that, for \n<jats:italic>u</jats:italic>∗/<jats:italic>u</jats:italic>∗<jats:sub><jats:italic>t</jats:italic></jats:sub> [les     ] 1.5, <jats:italic>f</jats:italic>(<jats:italic>z</jats:italic>) is approximately \nindependent of the particle density and decreases exponentially over a vertical scale \nlength <jats:italic>l</jats:italic><jats:sub><jats:italic>f</jats:italic></jats:sub>, that is about 3 to 4 times the estimated mean height of the particle \ntrajectories 〈<jats:italic>h</jats:italic>〉. Numerical simulations of saltating grains were computed using the \nmeasured probabilities of ejection velocities and the mean velocity profile of the air \nflow, but neglecting the direct effect of the turbulence. The calculated mean values \nof the impact velocities and the trajectory dimensions were found to agree with the \nmeasurements in the saltation range, where \n<jats:italic>u</jats:italic>∗/<jats:italic>u</jats:italic>∗<jats:sub><jats:italic>t</jats:italic></jats:sub> < 1.5. Similarly, in this range \nthe simulations of the horizontal flux profile and integral are also consistent with the \nmeasurements and with Bagnold's <jats:italic>u</jats:italic>∗<jats:sup>3</jats:sup> formula, respectively.</jats:p><jats:p>When <jats:italic>u</jats:italic>∗/<jats:italic>u</jats:italic>∗<jats:sub><jats:italic>t</jats:italic></jats:sub> [ges     ] 1.5, and \n<jats:italic>u</jats:italic>∗/<jats:italic>V</jats:italic><jats:sub><jats:italic>T</jats:italic></jats:sub> [ges     ] 1/10, where <jats:italic>V</jats:italic><jats:sub><jats:italic>T</jats:italic></jats:sub> \nis the settling velocity, a transition \nfrom saltation to suspension occurs. This is indicated by the change in the mean mass \nflux profile which effectively becomes uniform with height (<jats:italic>z</jats:italic>) up to the top of \nthe boundary layer. An explanation is provided for this low value of turbulence \nat transition relative to the settling velocity in terms of the random motion of \nthe particles under the action of the turbulence when they reach the tops of their \nparabolic trajectories. The experiments show that, as <jats:italic>u</jats:italic>∗/<jats:italic>u</jats:italic>∗<jats:sub><jats:italic>t</jats:italic></jats:sub> \nincreases from 1.0 to 1.9 the normalized mean vertical impact velocity \n〈<jats:italic>V</jats:italic><jats:sub>3<jats:italic>I</jats:italic></jats:sub>〉/<jats:italic>u</jats:italic>∗ decreases by nearly 60% to \nabout 0.6, which is less than 50% of the value for fluid particles. There is also a \ndecrease in the vertical and horizontal component of the ejection velocity to values \nof 0.8 and 2.3, which are much less than their values in the saltation regime. We \nhypothesize that at the transition from saltation to suspension the ejection process \nchanges quite sharply from being determined by impact collisions to being the result \nof aerodynamic lift forces and upward eddy motions.</jats:p>"}]}],"creator":[{"@id":"https://cir.nii.ac.jp/crid/1581980076326858880","@type":"Researcher","foaf:name":[{"@value":"K. NISHIMURA"}]},{"@id":"https://cir.nii.ac.jp/crid/1382825895629677441","@type":"Researcher","foaf:name":[{"@value":"J. C. R. HUNT"}]}],"publication":{"publicationIdentifier":[{"@type":"PISSN","@value":"00221120"},{"@type":"EISSN","@value":"14697645"},{"@type":"NCID","@value":"AA00698198"}],"prism:publicationName":[{"@value":"Journal of Fluid Mechanics"}],"dc:publisher":[{"@value":"Cambridge University Press (CUP)"}],"prism:publicationDate":"2000-08-25","prism:volume":"417","prism:startingPage":"77","prism:endingPage":"102"},"reviewed":"false","dc:rights":["https://www.cambridge.org/core/terms"],"url":[{"@id":"https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022112000001014"}],"createdAt":"2002-07-27","modifiedAt":"2019-06-07","relatedProduct":[{"@id":"https://cir.nii.ac.jp/crid/1050307280801840640","@type":"Article","resourceType":"学術雑誌論文(journal article)","relationType":["isReferencedBy"],"jpcoar:relatedTitle":[{"@language":"en","@value":"Estimating the effect of snowdrift formation on turbulent airflow and subsequent snowdrift around three types of fences"}]},{"@id":"https://cir.nii.ac.jp/crid/1360285706527321856","@type":"Article","resourceType":"学術雑誌論文(journal article)","relationType":["isReferencedBy"],"jpcoar:relatedTitle":[{"@value":"PIV measurements of saltating snow particle velocity in a boundary layer developed in a wind tunnel"}]},{"@id":"https://cir.nii.ac.jp/crid/1360285707321379200","@type":"Article","resourceType":"学術雑誌論文(journal article)","relationType":["isReferencedBy"],"jpcoar:relatedTitle":[{"@value":"Development of a large-eddy simulation coupled with Lagrangian snow transport model"}]},{"@id":"https://cir.nii.ac.jp/crid/1360306905643306240","@type":"Article","resourceType":"学術雑誌論文(journal article)","relationType":["isReferencedBy"],"jpcoar:relatedTitle":[{"@value":"Elucidation of spatiotemporal structures from high-resolution blowing-snow observations"}]},{"@id":"https://cir.nii.ac.jp/crid/1360567179756278272","@type":"Article","resourceType":"学術雑誌論文(journal article)","relationType":["isReferencedBy"],"jpcoar:relatedTitle":[{"@value":"Snow particle speeds in drifting snow"}]},{"@id":"https://cir.nii.ac.jp/crid/1360853567671347840","@type":"Article","resourceType":"学術雑誌論文(journal article)","relationType":["isReferencedBy"],"jpcoar:relatedTitle":[{"@value":"Computational fluid dynamics simulations of snow accumulation on infrared detection sensors using discrete phase model"}]},{"@id":"https://cir.nii.ac.jp/crid/1390282681437203968","@type":"Article","relationType":["isCitedBy"],"jpcoar:relatedTitle":[{"@value":"吹雪における雪粒子の衝突・反発・射出"},{"@language":"en","@value":"Impact, rebound and ejection of snow particles in drifting snow"},{"@language":"ja-Kana","@value":"フブキ ニ オケル ユキ リュウシ ノ ショウトツ ハンパツ シャシュツ"}]},{"@id":"https://cir.nii.ac.jp/crid/1390282681437204992","@type":"Article","relationType":["isCitedBy"],"jpcoar:relatedTitle":[{"@value":"吹雪の物理モデルの現状と課題"},{"@language":"en","@value":"Recent studies on physical model of blowing snow and future research directions"},{"@language":"ja-Kana","@value":"フブキ ノ ブツリ モデル ノ ゲンジョウ ト カダイ"}]},{"@id":"https://cir.nii.ac.jp/crid/1572261550291335808","@type":"Article","relationType":["isCitedBy"],"jpcoar:relatedTitle":[{"@language":"en","@value":"Visualization of Saltating Sand Particle Movement near a Flat Ground Surface"}]},{"@id":"https://cir.nii.ac.jp/crid/2051433317037089664","@type":"Article","resourceType":"学術雑誌論文(journal article)","relationType":["isReferencedBy"],"jpcoar:relatedTitle":[{"@value":"Development of a snowdrift model with the lattice Boltzmann method"}]}],"dataSourceIdentifier":[{"@type":"CROSSREF","@value":"10.1017/s0022112000001014"},{"@type":"CIA","@value":"30022892010"},{"@type":"OPENAIRE","@value":"doi_dedup___::4c695b2abe9f89914677c1c6b20645ed"},{"@type":"CROSSREF","@value":"10.1007/s12650-012-0156-8_references_DOI_Qwx8HyFcUDyxeHlMjPC03cC0QGr"},{"@type":"CROSSREF","@value":"10.1186/s40645-021-00449-0_references_DOI_Qwx8HyFcUDyxeHlMjPC03cC0QGr"},{"@type":"CROSSREF","@value":"10.5194/tc-18-4775-2024_references_DOI_Qwx8HyFcUDyxeHlMjPC03cC0QGr"},{"@type":"CROSSREF","@value":"10.1002/2014jd021686_references_DOI_Qwx8HyFcUDyxeHlMjPC03cC0QGr"},{"@type":"CROSSREF","@value":"10.1016/j.jweia.2018.09.027_references_DOI_Qwx8HyFcUDyxeHlMjPC03cC0QGr"},{"@type":"CROSSREF","@value":"10.1016/j.coldregions.2020.103167_references_DOI_Qwx8HyFcUDyxeHlMjPC03cC0QGr"},{"@type":"CROSSREF","@value":"10.1016/j.jweia.2025.106089_references_DOI_Qwx8HyFcUDyxeHlMjPC03cC0QGr"}]}