<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">Dear Soft Matter Colleagues and Friends,</font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal; min-height: 14px;"><font face="HelveticaNeue" class=""><br class=""></font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">On Friday 14 May 2021 at 9:30 AM we are hosting a seminar during which</font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal; min-height: 14px;"><font face="HelveticaNeue" class=""><br class=""></font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class=""><b class="">Ahmad Ababaei </b>(Institute of Meteorology and Water Management –
National Research Institute)</font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal; min-height: 14px;"><font face="HelveticaNeue" class=""><br class=""></font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">will give a talk</font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal; min-height: 14px;"><b style="font-family: HelveticaNeue;" class=""><span lang="EN-US" class=""><br class=""></span></b></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal; min-height: 14px;"><b style="font-family: HelveticaNeue;" class=""><span lang="EN-US" class="">T</span></b><b style="font-family: HelveticaNeue;" class="">he </b><b style="font-family: HelveticaNeue;" class=""><span lang="EN-US" class="">impact </span></b><b style="font-family: HelveticaNeue;" class="">of </b><b style="font-family: HelveticaNeue;" class=""><span lang="EN-US" class="">lubrication forces and short-range non-continuum
molecular effects on the collision statistics of cloud droplets in homogeneous
isotropic turbulence </span></b></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal; min-height: 14px;"><font face="HelveticaNeue" class=""><br class=""></font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><b class=""><font face="HelveticaNeue" class="">Abstract</font></b></div><div class="" style="text-align: justify; margin: 0px; font-stretch: normal; line-height: normal;"><div class="" style="text-align: start;"><span lang="EN-US" style="font-family: HelveticaNeue;" class=""><br class=""></span></div><div class="" style="text-align: start;"><span lang="EN-US" style="font-family: HelveticaNeue;" class="">The dynamics of inertial
particles in homogeneous isotropic turbulence is investigated, under one-way
momentum coupling, using a new computational approach. The method incorporates </span><span style="font-family: HelveticaNeue;" class="">the
long-range many-body aerodynamic interactions</span><span lang="EN-US" style="font-family: HelveticaNeue;" class=""> with the </span><span style="font-family: HelveticaNeue;" class="">short-range lubrication forces</span><span style="font-family: HelveticaNeue;" class=""> </span><span lang="EN-US" style="font-family: HelveticaNeue;" class="">and the </span><span style="font-family: HelveticaNeue;" class="">non-continuum molecular effects.</span></div><div class="" style="text-align: start;"><p class=""><font face="HelveticaNeue" class="">The implementation couples Hybrid Direct Numerical Simulations (HDNS) with
the analytical solutions of two rigid spheres moving in an unbounded fluid.
Merging of these two approaches allows us to jointly represent two important
effects usually neglected in the previous studies: (i) HDNS accurately captures
the effect of many-body interactions among widely separated droplets, <span lang="EN-US" class="">while</span> (ii) the analytical
solution for two interacting rigid spheres in low-Reynolds-number flows allows
us to represent the lubrication effects.<span lang="EN-US" class=""> In case of very short separation distances between two droplets, the
non-continuum correction to the lubrication forces is additionally considered. <o:p class=""></o:p></span></font></p><p class=""><font face="HelveticaNeue" class="">Concerning the velocity field seen by the particles, the algorithm switches
from the flow solution in terms of HDNS to analytical formulae when the
separation distance between particles becomes comparable to their average
radius. Switching to the analytical solutions is made considering that the
standard HDNS is unable to correctly represent the short-range interactions,
since this method is based on the superposition of the Stokes solutions for
single spheres.<o:p class=""></o:p></font></p><p class=""><font face="HelveticaNeue" class="">The results show that for the turbulent kinetic energy dissipation rates
typical of atmospheric clouds, the radial relative velocities (RRV) of the
droplets increase, and the radial distribution function (RDF) decreases in the
near-contact region if the lubricative forces are taken into account. These
changes are more pronounced when the effect of gravity is considered. Away from
the contact region, however, there is not much change in RRVs and RDFs. For
turbulent clouds with lower dissipation rates lubrication forces significantly
enhance the average RRV in the limit of low Stokes number. This enhancement,
however, is statistically insignificant because the number of particle pairs at
close proximity is very small. The effect of mass loading on the collision
statistics is also investigated, demonstrating an increase in RRV and a
reduction in RDF with the droplet concentration.<o:p class=""></o:p></font></p>
<!--EndFragment--></div></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal; min-height: 14px;"><font face="HelveticaNeue" class=""><br class=""></font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">The seminar will be conducted on Zoom</font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><a href="https://us02web.zoom.us/j/82784273907" class=""><font face="HelveticaNeue" class="" color="#0433ff">https://us02web.zoom.us/j/82784273907</font></a></div></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">and will begin at <b class="">9:30AM</b>. </font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal; min-height: 14px;"><font face="HelveticaNeue" class=""><br class=""></font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">Maria Ekiel-Jeżewska</font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">Maciej Lisicki</font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">Marek Napiórkowski</font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">Piotr Szymczak</font></div><div class="">
<div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="">--</div><div class="">Dr Maciej Lisicki</div><div class="">Institute of Theoretical Physics | Faculty of Physics</div><div class="">University of Warsaw</div><div class=""><a href="http://softmatter.fuw.edu.pl" class="">softmatter.fuw.edu.pl</a></div><div class=""><br class=""></div><div class=""><br class=""></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div><div class=""><br class=""></div><br class="Apple-interchange-newline">
</div>
<br class=""></body></html>