{"id":12,"date":"2016-09-19T00:53:57","date_gmt":"2016-09-18T23:53:57","guid":{"rendered":"http:\/\/wp.cs.ucl.ac.uk\/flume\/?page_id=12"},"modified":"2021-03-21T20:14:31","modified_gmt":"2021-03-21T20:14:31","slug":"research","status":"publish","type":"page","link":"https:\/\/wp.cs.ucl.ac.uk\/flume\/research\/","title":{"rendered":"Research"},"content":{"rendered":"

Biofluids and cardiovascular engineering<\/span><\/strong><\/p>\n

Our interest is in haemodynamics in physiology and disease. Our work covers both the macro\u00a0and microcirculation. We conduct in vitro experiments to understand blood flows in\u00a0disease and develop biophysical markers and diagnostics for disease.<\/p>\n

Our macrocirculation work in collaboration with Prof Diaz (\u00a0MUSE<\/a>\u00a0) \u00a0and vascular surgeons deals with \u00a0complex vascular pathologies such as\u00a0aortic dissection <\/span><\/strong>and arteriovenous malformation.\u00a0<\/span><\/strong>We combine in vivo in vitro and in silcio tools to study the hemodynamics in such pathologies.<\/p>\n

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\"\"We have developed a unique experimental facility to recreate patient specific<\/span><\/strong>, physiological blood flows in the lab.<\/p>\n

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We combine these with anatomically\u00a0realistic 3D printed phantoms of the vessel of interest \u00a0obtained from patient CT scans and optical flow diagnostic techniques such as PIV to resolve the flow characteristics of the pathology. This information \u00a0helps to understand disease progression, aid clinical intervention decisions and also inform and validate numerical modelling (CFD) approaches for personalised medicine (see eg\u00a0Bonfanti et al 2020,\u00a0ABME<\/a>).\u00a0<\/em><\/p>\n

To better understand microvascular flow<\/span> <\/strong>phenomena and develop<\/span><\/span> blood diagnostics<\/span><\/strong> we have developed in vitro approaches combining microfludics, microPIV<\/span> techiques and advanced image processing techniques to study\u00a0\u00a0RBC transport\u00a0<\/span>in small channels with application to physiology and disease.\"\"<\/p>\n

Our interest is on the effects of \u00a0RBC aggregation<\/span><\/strong> and deformability<\/span><\/strong> on microhaemodynamics. \u00a0We have studied such flows in \u00a0bifurcating microfludic channels<\/span> <\/strong>mimicking the microcirculation as well as \u00a0complex geometries such as those found in medical devices. (see eg Sherwood et al, PLOS One<\/a>)<\/p>\n

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Comp<\/strong><\/span>le<\/strong><\/span>x fluids<\/strong><\/p>\n

Our work \u00a0focusses on elastoinertia instabilities of viscoelastic fluids and the behaviour of \u00a0structured fluids such as particle suspensions; in\u00a0particular on linking the microscopic behaviour of such suspensions to macroscopic flow behaviour.<\/span><\/p>\n

Elastoinertia \u00a0 instabilities<\/strong>. \u00a0Using<\/span>\u00a0<\/span><\/span>a Taylor-Couette flow of polymer solutions we have \u00a0probed elastoinertia instabilities \u00a0and in particular the transition to elastoinertia turbulence (EIT)<\/strong><\/span> for a range of Boger and \u00a0shear thinning fluids. We are interested on the mechanisms leading \u00a0to EIT, the effects of shear thinning or added particles.\u00a0<\/span><\/p>\n

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Space-Reynolds flow map in a Taylor Couette flow of a Newtonian elastic fluid (Boger). (see eg Lacassagne et al 2020<\/a>, Cagney et al 2020<\/a>).<\/p>\n

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Particle Suspensions<\/span>:<\/span> <\/strong>\u00a0We combine a suite of techniques \u00a0such as rheology, rheo-optics, microlfuidics and PIV to probe the behaviour of<\/span>\u00a0\u00a0dense suspensions of non Brownian silica particles<\/span> \u00a0in complex formulations<\/span> \u00a0(as part of our EPSRC Future Formulations\u00a0<\/span>programme CORAL \u00a0in collaboration with UCL Chemical Engineering, UCL Mathematics)\u00a0<\/span>as<\/span>\u00a0well as<\/span> cell suspensions<\/span> such as RBCs and algae<\/span>.\"\"<\/p>\n

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Using commercial silica particles<\/span> used in industry as abrasives or fillers, suspended in non aqueous and no Newtonian matrices we were able to probe frictional<\/span> and adhesive mechanisms<\/span> of \u00a0shear thinning, develop routes to tune rheology<\/span> and examine the effects of non-Newtonian matrices \u00a0on suspension rheology (see eg Papadopoulou, 2020<\/a>)<\/p>\n

\"\"Cellular \u00a0suspensions.\u00a0<\/span>\u00a0Using idealised microfluidic geometries to mimic microvascular bifurcations,\u00a0\u03bcPIV and image processing we have simultaneously characterised the flow field and cell distribution of RBCs in bifurcations in the presence\u00a0of aggregation (Sherwood et al 2012, 2014).\u00a0We have also \u00a0quantified \u00a0RBC aggregation in situ (Kaliviotis et al, 2016) and examined the partitioning of aggregates \u00a0 (Kaliviotis et al 2017<\/a>) and \u00a0their effect on local viscosity (see fig below and\u00a0Kaliviotis et al 2018<\/a>).<\/p>\n

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\"\"We have also<\/span>\u00a0 <\/span>experimented with algae suspensions,\u00a0looking at their rheological behaviour of algae suspensions and its impact on downstream processing of algae biomass. Working closely with with Dr Mike Allan form Plymouth Marine Laboratories \u00a0we have investigated the effects of motility<\/span> and mor<\/span><\/span>ph<\/span>ology<\/span> on rheology by looking at flagellated (T<\/span>etraselmis chuii)<\/em> and high aspect ratio species (<\/span>Phaedodactylum\u00a0<\/em>tricornutum<\/i>) in comparison to round, non motile species (<\/span>Chlorella sp<\/em>). see\u00a0<\/span>(Cagney et al, <\/a>\u00a02017).<\/a><\/p>\n

Vortex dynamics and fluid structure interaction<\/span><\/strong><\/p>\n

We have experimented extensively with flows past cylinders<\/strong><\/span> and cylinder arrays<\/span><\/strong> looking at the flow field and vortex\u00a0shedding characteristics \u00a0in flows past staggered and\u00a0in line arrays of cylinders. We also looked at the effects\u00a0\u00a0of external flow forcing<\/span><\/strong> on the wake of a single \u00a0cylinder and cylinder arrays (Konstantinidis et al 2004, 2005, 2007) and explored the possibility of using flow oscillations as a process intensification tool. Our forced oscillations\u00a0work shed light to a number of fascinating phenomena such as lock in, vortex shedding modes<\/span> and mode switching<\/span> and subsequently gave rise to research into vortex induced vibrations.<\/p>\n

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Our work in \u00a0this field focuses primarily on streamwise cylinder oscillations<\/span><\/strong>.Using \u00a0time resolved PIV techniques we have been able to simultaneously capture the\u00a0amplitude response and wake modes<\/span>\u00a0of the oscillating cylinder for a range of reduced velocities.\u00a0Also to\u00a0study\u00a0the effect of a second degree of freedom on the\u00a0measured response\u00a0(<\/span>see eg Cagney & Balabani, 2014<\/a>).<\/span><\/p>\n

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Our current research focusses on the\u00a0effect of body shape<\/span><\/strong>\u00a0 (see Cagney 2019<\/a>)\u00a0as well as the\u00a0onset of vortex shedding under confinement<\/strong><\/span>\u00a0(i.e. in confined flows past micropins, see Zhang et al 2019<\/a>).<\/p>\n

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\nhttp:\/\/wp.cs.ucl.ac.uk\/flume\/wp-content\/uploads\/sites\/33\/2020\/03\/Video_15s.mp4<\/a><\/video><\/div>\n
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Mixing and transport\u00a0<\/strong><\/span>phenomena<\/b><\/span><\/p>\n

Mixing is ubiquitous in nature and engineering. Understanding transport phenomena can aid the design of processes and manufacturing. Our research focusses on quantifying mixing in vortical and swirling flows using PIV\/LIF techniques<\/span>. We are applied these techniques to study intra-and inter vortex mixing in Taylor Couette flows (<\/span><\/span>Dusting-Balabani, 2009; Imomoh et al 2010), mixing through bluff body wake oscillations (Cagney-Balabani, 2016) as well as micro droplet mixing processes for diagnostics (Ma et al 2014, 2015). We currently extend this work in non-Newtonian<\/span> flows.<\/span><\/p>\n

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LIF and PIV studies in a Taylor Couette flow (Dusting & Balabani, ChemEngSci, 2009).<\/em><\/p>\n

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Mean concentration fields in the wake of an \u00a0oscillating cylinders showing the influence of vortex shedding mode on mixing (Cagney & Balabani, 2016)<\/em><\/p>\n

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Microfluidics\u00a0<\/span><\/strong><\/p>\n

\"\"Our work focusses on the development and characterisation of fluidic systems for point of care diagnostics and drug delivery applications. For example, we have studied the flow inside microdroplets, explored the microenvironment and the deformation of compound droplets under sheath flow focusing conditions relevant to cell encapsulation, in collaboration with Dr Shaohua Ma and Prof Huck. This work has featured on the cover of Lab on a Chip (see eg\u00a0Ma et al 2014<\/a>) \u00a0Ma et al 2015)<\/a>\u00a0<\/em><\/p>\n

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In collaboration with two different groups, \u00a0UCL Division of Surgery (Dr Wenhui Song) and \u00a0University of Cape Town (South Africa) we \u00a0have combined microfluidics with various types of hydrogels to study the micro flow characteristics of novel injectates for tissue engineering applications (see eg Chen et al 2018<\/a>, \u00a0Ngoepe et al, 2019)<\/a><\/p>\n

Current work includes microfludic studies of microswimmers \u00a0and on detecting organ rejection.<\/p>\n","protected":false},"excerpt":{"rendered":"

Biofluids and cardiovascular engineering Our interest is in haemodynamics in physiology and disease. Our work covers both the macro\u00a0and microcirculation. We conduct in vitro experiments to understand blood flows in\u00a0disease and develop biophysical markers and diagnostics for disease. Our macrocirculation … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":95,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":[],"_links":{"self":[{"href":"https:\/\/wp.cs.ucl.ac.uk\/flume\/wp-json\/wp\/v2\/pages\/12"}],"collection":[{"href":"https:\/\/wp.cs.ucl.ac.uk\/flume\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/wp.cs.ucl.ac.uk\/flume\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/wp.cs.ucl.ac.uk\/flume\/wp-json\/wp\/v2\/users\/95"}],"replies":[{"embeddable":true,"href":"https:\/\/wp.cs.ucl.ac.uk\/flume\/wp-json\/wp\/v2\/comments?post=12"}],"version-history":[{"count":48,"href":"https:\/\/wp.cs.ucl.ac.uk\/flume\/wp-json\/wp\/v2\/pages\/12\/revisions"}],"predecessor-version":[{"id":440,"href":"https:\/\/wp.cs.ucl.ac.uk\/flume\/wp-json\/wp\/v2\/pages\/12\/revisions\/440"}],"wp:attachment":[{"href":"https:\/\/wp.cs.ucl.ac.uk\/flume\/wp-json\/wp\/v2\/media?parent=12"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}