{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"3198395f6859c43f963d79e997ced5c54629644b9944c1aee4f83384bfbcf32f","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["334a0ed2845fcb864ceff226ac3480c2238a82201957cb3bc61fef48adb6c1e7","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"87e2d70e4c97716d558cbf07a94283fdaf86a543bc3b26f606b66e686aeb40ce","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":["ai:gpt-5.5"],"external_id":"fluid.contact-lines.air-entrainment-threshold","kind":"well-posed","literature_status":"partially-resolved","n":"2","parents":[],"plain":"When a plate or tape is pushed quickly into a liquid, above a critical speed the liquid can no longer wet the solid and a thin air film is dragged in, which ruins coatings. What sets that critical speed?","posed_since":"","precise":"For a solid plunging at speed $U$ into a liquid of viscosity $\\eta$ and surface tension $\\gamma$, surrounded by gas of viscosity $\\eta_g$ and pressure $p$, predict the critical capillary number $\\mathrm{Ca}* = \\eta U*/\\gamma$ for dynamic wetting failure, including its dependence on the viscosity ratio $\\eta_g/\\eta$, on gas rarefaction when the mean free path approaches the air-film thickness, and on the large increase of $\\mathrm{Ca}*$ when the flow pushes the liquid against the solid (curtain coating). An answer predicts $\\mathrm{Ca}*$ within experimental error for $\\eta_g/\\eta$ from $10^{-6}$ to $10^{-2}$ and across reduced gas pressures.","problem_ref":"334a0ed2845fcb864ceff226ac3480c2238a82201957cb3bc61fef48adb6c1e7","references":"","settled_by":"A comparison of measured $\\mathrm{Ca}*$ for plunging plates and curtain coating over wide viscosity ratios and gas pressures with a single model of the gas film and the contact line.","status_note":"Lubrication models that include gas viscosity capture the weak viscosity-ratio dependence for simple plunging; the roles of gas rarefaction and of flow assistance remain unsettled as of 2026 (not re-verified for 2024-2026).","title":"Threshold speed for air entrainment in forced wetting","topic_ref":null},"content_withheld":"false","files":[],"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"71d8262e87efda11b4021e3dca831682b497536c30a52f76713ba051bf446bec","schema":"pubphys.attested/1"},"id_token":null,"id_token_withheld":"false","envelope":{"attested_hash":"7bd72876f79324cfbee07a485210ba32b4561349482d46b8cc8c7b6958e0b20b","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"NrqDcAVNY0U3x8puy5NnmEbGJaIsGJ-cG573Tdn_vsi0ztoJ6aTS_TkSEMadc69eoUKTMYsMNHR6_3E8mQpzAA"},"schema":"pubphys.envelope/1"},"ots":{"attested":["AE9wZW5UaW1lc3RhbXBzAABQcm9vZgC_ieLohOiSlAEIe9codveTJM--4HpIUhC6MrRWE0lILUa4zIx7aVjgsgvwIHvfAAQAr21-Ev1cT_qqbaQBkHYKvOC5WWr7QTGk3A_yCPAg2bg4bdyOfHgEi959f66fcoZqjit9HgIevuMeOkqLXNMI8SDU6qZAxaHsF9gv2NOlJYjhH5XdjinPiee0s-Pd642yegjwIPLx5CzCVVr9-Th3oYKWPK6hGT-oU_cg3HNIeLK_lx1HCPAg7bABo6WZQ2eyXXr99XBQlAA_1Zsqrj616XdoLbfAldoI8SDRVwDUbKiHkLGRwIBP7Zb9IC0P3TOIOPuGjC32wpU2WgjxINa0voVB5dVvA8mG3aK_q_H4RbvesCgQAIqtbZgmnzDbCPAgXx45yhBgitlxXZoPiY801JhflemOgnxVewLKiGj6hiYI8CCCFfNrg2ZeB51PNa84j-z6Sin0AxT6aP9r7HupgUKbMwjxICknnLxa8xs8qmAdhtb0NnANbtwYyrlRTgqcMVLLl8ogCPEgHd9u6OIGCvUV12A1B1xdiOprSJ-4w0cqwfe7CzVX5HsI8CDQo_sIWZiWXaTGRSQBLmU-lHJKskYKqsjO1r02DhB8LAj_8Ajn9YmozHwo9QjwEJ46aM9ZDv3TdtqV3ZbRsNgI8SBOF8pILGf1kodr5MKmQs6Cd93joraGn3g6UPt_-kewPwjwIOG-gmM7bd_eR4AiDMNfluS3xvr7vicLR-sCBr5qtG2cCPAgrVNFrCoeQcCxhlmnE0BzHgR8HQpZAlfqzDDFzfWb8GUI8QRq0WWT8AjZJ2cF_c7k8ACD3-MNLvkMjiwraHR0cHM6Ly9ib2IuYnRjLmNhbGVuZGFyLm9wZW50aW1lc3RhbXBzLm9yZ_AI9ZMS1zxd7IEI8BDd00WgJZ0RncsC1Fyai_4aCPEgvxMFrnu7F05IW5INiraQ3OVEYMjNx6JfBxw1Q4jPLi4I8QRq0WWS8Ag2zxPAtI5JsP8Ag9_jDS75DI4uLWh0dHBzOi8vYWxpY2UuYnRjLmNhbGVuZGFyLm9wZW50aW1lc3RhbXBzLm9yZwjxIHAnv4KFFf4uiYEFJvLxiMxSyz8VowJP4roTfDD9h7bICPAgj5tgvbNF7mxSP4jGGE66ezUFRLnI4g1VTkvuV4VtCPAI8CCxlc1HuKORuHgn7DYIYcDhc4oo99OkTWBEvddBypoa7AjwIFcjjaF8kDNDYCZGaNISlRjvX-I7in-QNwsr4JYQbFJvCPAgnl0k4gs7LuY5i1umiHO-J7My3uBThLJUWQoY9LdVSrQI8SA6-Ft11_K_GqMNWYhkVsVqCFvXSYbp4S8JoLsLBnUzvgjxIBC8_mAE7JBP35SNxDBcG7joLJwURpMxdV2vSO64_jEOCPEge04Coj1xSi7CE8UwqiBGNhPyZ5QdD_YZwn-heSdObU4I8SBgdDSgr3VUx1j8m_pK7-OzMwwFgXeLy43ujffCv-hf5AjwIMl-PnAt4xjoBEVU4-nkyN0NKRa9AvX4kEMfllFyIJS9CPFZAQAAAAHz4rV-uwQFg02bVnEMUFgpIdGKjM4tWuID1kTVnrjisAAAAAAA_v___wJURAIAAAAAABYAFBFys2oc0-U-bYrC3VulGLzND5fbAAAAAAAAAAAiaiDwBHLTDgAICPEgMJIBYi46xOIuFDwzJ9nOx14ngW5HbglUf65ORpkoIYcICPAgHgGWEGCDHWgscwT92NOoJ7s-ezbPkyiWr2RnYZDC_dwICPAgtffMyyLu-MscJsDc0dzwGspwSrrmvVAnMNgsgWhHClgICPAgMUl1OfBDUwhp5VZjHwVA0nuz1F5HZTUJCHAnM1L1F3MICPAgStK7UWpnrUueV5EaE7uE0y6BLMp6EANmrbhrTqEBZu8ICPAg5LVW7IHtUL5mNOvPx1hOTfLMmqlQ7t9EFW-KDtrISIQICPAgABgXZ6upFU8qiDQKFtQFpqkjKwl0PsxM4JUjVLlDKbkICPAgEwb96FiOhjlbwI8GFZQ4a5GXwxs4bUdqVOMKrtBWV30ICPEgqBg-wp0c8CAPV9k6J7wIa9_GtQfpWmhpE1zqFZyi2pQICPAg2pZLTVPGJbriiz0UhMytYDVYAXOgQnWDcrMOewK9O8cICPEgxm3QwzbvT4siJzubQGnST67bWv-exYwSPP1KDi7CaUwICPEgm6udUudfjUaM0gUFTylKGDMypj7ptMTG0zmxd_T5yTcICPAgMpOInkjFCVp1pOZhfZnyPAl8hdWGmHzQcrGLgLwSKLgICAAFiJYNc9cZAQPzpjs"],"envelope":["AE9wZW5UaW1lc3RhbXBzAABQcm9vZgC_ieLohOiSlAEIuBEtQcgd1j-ybMRHmZhImBxAKyu22g_inFXqmSknj-fxILe8I9DE9CpKhOjlR1MPJ8TjjMdSNQaHnm1d8vIv571aCPAgAkCBzDlfGD1bW6cWvoUfWonLj7Fn1qmRXeX3KPvllPwI8SCtlCvrD7WcOQFhUyI2as9hhSzsQht-IzT_TLb2XpwFfQjxIHXfqox4LCF7n4_B0vSSy5U5IsIQ3pXm3rbRAErBzp7DCPAgwLL318MtqpENrlg2TeT23bXVfgIOZhPvBTs-o2katisI8SDPyR82cyCdu8iLIooUAyQsWMLMoZplkabuvCEYSEZqagjxIDwyhdMMcC9HUXvmnOqr-4hz0bthwNRePVXecoiwxma1CPAgsToia8UFTWcgAGCYERTkLASNsxtWD-53uc5ktQ4BIIgI8SDArwsGYVuomKH_DJiJGziPwECn7skqn20TGM58Ezco0wjwIIgwugvlgSNOmTWMhquqetKjeLf0x7d1a1MH4KU52JbFCPAg3mczMYDKOd7Nhf3ojA9ZvuTsN66Y1NnyYTp9j8GKQNwI8SCvAiiN-Hrv7IEejd8wdUihoozu5KOvpoBFJ0vg3UnGAQj_8Ajn9YmozHwo9QjwEJ46aM9ZDv3TdtqV3ZbRsNgI8SBOF8pILGf1kodr5MKmQs6Cd93joraGn3g6UPt_-kewPwjwIOG-gmM7bd_eR4AiDMNfluS3xvr7vicLR-sCBr5qtG2cCPAgrVNFrCoeQcCxhlmnE0BzHgR8HQpZAlfqzDDFzfWb8GUI8QRq0WWT8AjZJ2cF_c7k8ACD3-MNLvkMjiwraHR0cHM6Ly9ib2IuYnRjLmNhbGVuZGFyLm9wZW50aW1lc3RhbXBzLm9yZ_AI9ZMS1zxd7IEI8BDd00WgJZ0RncsC1Fyai_4aCPEgvxMFrnu7F05IW5INiraQ3OVEYMjNx6JfBxw1Q4jPLi4I8QRq0WWS8Ag2zxPAtI5JsP8Ag9_jDS75DI4uLWh0dHBzOi8vYWxpY2UuYnRjLmNhbGVuZGFyLm9wZW50aW1lc3RhbXBzLm9yZwjxIHAnv4KFFf4uiYEFJvLxiMxSyz8VowJP4roTfDD9h7bICPAgj5tgvbNF7mxSP4jGGE66ezUFRLnI4g1VTkvuV4VtCPAI8CCxlc1HuKORuHgn7DYIYcDhc4oo99OkTWBEvddBypoa7AjwIFcjjaF8kDNDYCZGaNISlRjvX-I7in-QNwsr4JYQbFJvCPAgnl0k4gs7LuY5i1umiHO-J7My3uBThLJUWQoY9LdVSrQI8SA6-Ft11_K_GqMNWYhkVsVqCFvXSYbp4S8JoLsLBnUzvgjxIBC8_mAE7JBP35SNxDBcG7joLJwURpMxdV2vSO64_jEOCPEge04Coj1xSi7CE8UwqiBGNhPyZ5QdD_YZwn-heSdObU4I8SBgdDSgr3VUx1j8m_pK7-OzMwwFgXeLy43ujffCv-hf5AjwIMl-PnAt4xjoBEVU4-nkyN0NKRa9AvX4kEMfllFyIJS9CPFZAQAAAAHz4rV-uwQFg02bVnEMUFgpIdGKjM4tWuID1kTVnrjisAAAAAAA_v___wJURAIAAAAAABYAFBFys2oc0-U-bYrC3VulGLzND5fbAAAAAAAAAAAiaiDwBHLTDgAICPEgMJIBYi46xOIuFDwzJ9nOx14ngW5HbglUf65ORpkoIYcICPAgHgGWEGCDHWgscwT92NOoJ7s-ezbPkyiWr2RnYZDC_dwICPAgtffMyyLu-MscJsDc0dzwGspwSrrmvVAnMNgsgWhHClgICPAgMUl1OfBDUwhp5VZjHwVA0nuz1F5HZTUJCHAnM1L1F3MICPAgStK7UWpnrUueV5EaE7uE0y6BLMp6EANmrbhrTqEBZu8ICPAg5LVW7IHtUL5mNOvPx1hOTfLMmqlQ7t9EFW-KDtrISIQICPAgABgXZ6upFU8qiDQKFtQFpqkjKwl0PsxM4JUjVLlDKbkICPAgEwb96FiOhjlbwI8GFZQ4a5GXwxs4bUdqVOMKrtBWV30ICPEgqBg-wp0c8CAPV9k6J7wIa9_GtQfpWmhpE1zqFZyi2pQICPAg2pZLTVPGJbriiz0UhMytYDVYAXOgQnWDcrMOewK9O8cICPEgxm3QwzbvT4siJzubQGnST67bWv-exYwSPP1KDi7CaUwICPEgm6udUudfjUaM0gUFTylKGDMypj7ptMTG0zmxd_T5yTcICPAgMpOInkjFCVp1pOZhfZnyPAl8hdWGmHzQcrGLgLwSKLgICAAFiJYNc9cZAQPzpjs"]},"log":{"leaf_index":"3256","tree_size":"3804","proof":["a86d4577a8389123aa0ebb1678c1b64f935398a3275c6d74c9b6ad66bc856e3f","8f82749aeb836926a3dce890b9b13ebd4b4e429c235f788ae39fea68cb8293c3","082c2b5d70976b8670393fc95c6b6730593990b672f812654b3c89948f07fbe2","9b8ada902a979e5cf3c7fbf8be7f2e62e2015fd7ba862796a20c19d7d683375b","0474a467c9ee8e75e01e4804ccd534fa307ed958ff5de0b0d3c136242a7f178d","51747b36322b0d617609b618a645021cf4cc14a8f75b6309c7b53c622df86ebc","bcad5f24fa771bddd97e4cf7acbfd5d77087bad3e6f94962b11c748e4aeb9cd0","1ed62395399131ae4d5b365e81f741fbe796392ae81801387a716b09dc35a694","48906313613fdfddd2bd907650210a7f3e59ccb380a2b862e892089f41bcdced","98b5a14b42b3a202b6ef825f66833fa505601404c4c0f14575f3ec922607a858","af34d80d0065c0ab502282775e865492e2cb49c9493f4594d63ba5577922854a","3c578dccc15502c5f3efe228cadc99fee76ab536ed01f66b14d316fdcc157429"],"checkpoint":"pubphys.com/log/v1\n3804\nAK6t4qgu96+M9wScTrIlsJ10d/zhKVEtYguyM3aeJvo=\n\n— pubphys.com/log/v1 JFPwIPP8EtoxgcsQg7V7CwIdL4UKPqJtpv+eB8sFNJjyQHIdyA1VabmBsPyLqq2bLxJPn57rA6fQi8y0QDDjRXHvlQg=\n","promise":"pubphys.com/log/v1 promise\n5c6b397d3609ec401d74ff6666398291212731eca9cbb4fde1b36b90b64613ce\n3256\n2026-10-15T23:43:57Z\n2026-10-16T01:43:57Z\n\n— pubphys.com/log/v1 JFPwILUDWqMmTrxa70HcdCmj1ZiVryk3W0xt0TjnFnfLC9MdzvYDwlSWcdKO59oIcEXz6d+9RmWHqMrygkItDBziGAk=\n"},"orcid_key_evidence":[],"attesting":null}