Mature heart valves are complex structures consisting of three highly organized extracellular matrix layers primarily composed of collagens, proteoglycans and elastin. Collectively, these diverse matrix components provide all the necessary biomechanical properties for valve function throughout life. In contrast to healthy valves, myxomatous valve disease is the most common cause of mitral valve prolapse in the human population and is characterized by an abnormal abundance of proteoglycans within the valve tri-laminar structure. Despite the clinical significance, the etiology of this phenotype is not known. Scleraxis (Scx) is a basic-helix-loop-helix transcription factor that we previously showed to be required for establishing heart valve structure during remodeling stages of valvulogenesis. In this study, we report that remodeling heart valves from Scx null mice express decreased levels of proteoglycans, particularly chondroitin sulfate proteoglycans (CSPGs), while overexpression in embryonic avian valve precursor cells and adult porcine valve interstitial cells increases CSPGs. Using these systems we further identify that Scx is positively regulated by canonical Tgfβ2 signaling during this process and this is attenuated by MAPK activity. Finally, we show that Scx is increased in myxomatous valves from human patients and mouse models, and overexpression in human mitral valve interstitial cells modestly increases proteoglycan expression consistent with myxomatous mitral valve phenotypes. Together, these studies identify an important role for Scx in regulating proteoglycans in embryonic and mature valve cells and suggest that imbalanced regulation could influence myxomatous pathogenesis.

Many chemical engineering processes involve the suspension of solid particles in a liquid. In dense systems, agitation leads to the formation of a clear liquid layer above a solid cloud. Cloud height, defined as the location of the clear liquid interface, is a critical measure of process performance. In this study, solid-liquid mixing experiments were conducted and cloud height was measured as a function operating conditions and stirred tank configuration. Computational fluid dynamics simulations were then performed using an Eulerian-Granular multiphase model. The effects of hindered and unhindered drag models and turbulent dispersion force on cloud height were investigated. A comparison of the experimental and computational data showed excellent agreement over the full range of conditions tested.

The present work concerns the development of a comprehensive model capability in ANSYS CFD software FLUENT towards modeling of multiphase flows in porous media with targeted applications in reservoir/well analyses. The modeling approach is based on the Eulerian multifluid model. Porous media are modeled by both Superficial and Physical Velocity formulation with embedded sub-models to account for the resistance sink, relative-permeability and capillary pressure effect. An advanced numerical algorithm has been developed to achieve time-step and mesh independent solutions as well as to satisfy the physical constraints/limits. In particular, the resistance sinks are rearranged and linearized to ensure numerical stability and to handle mathematically infinite resistance caused by possible zero relative permeability. The capillary pressure and body forces are implicitly treated to enhance solver robustness. The multiphase porous medium model is compatible with all the numerical schemes and solvers (iterative and non-iterative) available in FLUENT. The present model has been applied to simulate 1D, 2D and 3D transient oil-water two-phase flows mimicking the conditions in reservoirs and wells. The solutions are time-step and grid independent, and successfully reproduce the flow characteristics and physical limits. The solvers are fast and robust, allowing the time step to be as large as 2 hours for a reservoir setting with the flow physical time in 2–20 years. The model capability shows great promises for reservoir and well performance analysis.

Modeling cavitation phenomenon can be a challenging prospect for numerical solvers because the available cavitation models require a fine-tuning of model parameters and a good quality mesh in cavitating zones. Cavitation often occurs in complex geometries such as nozzle injection systems, marine propellers or gear pumps and creating a good quality mesh in such geometries need high skill and enough time. Overset mesh simplifies the overall meshing process in complex geometries by allowing separately generated good quality component meshes, which later overlap on each other to form actual flow domain. The aim of this study is to validate the accuracy of the overset method for cavitating flow problems using a multi-phase RANS flow solver and a homogeneous mixture model. Cavitating flow inside a circular throttle injection system is validated against experiment where mass flow rates at the outlet are compared at different inlet pressures. Flow past a fully submerged wedge-shaped hydrofoil is analysed for different cavitation numbers and multiple angles of attack, where cavity shapes for both overset and non-overset meshes are compared with experimental images. Furthermore, supercavitation phenomenon for the flow past a circular disk is investigated where cavity length and cavity radius are validated against the empirical correlations proposed by different authors. This study also highlights the best practices for Schnerr-Sauer and Zwart-Gerber-Belamri cavitation models available in ANSYS Fluent with overset mesh.

The understanding of two-phase gas-liquid flows is of utmost importance in a large range of industrial applications, including the petrochemical, pharmaceutical, biochemical, nuclear, and metallurgical industries. At ANSYS, significant effort is being made in assessing the physical force models present in both FLUENT and CFX. This includes the investigation of the interfacial closures (drag, lift, wall lubrication, turbulent dispersion, and virtual mass), heat and mass transfer, cavitation, wall boiling, population balance approaches, bubble breakup and coalescence, and turbulence modeling. This assessment is being done with the objective to conduct an audit/ validation of the current models, features, and capabilities, as well as the identification and closing of gaps and differences between CFX and FLUENT. The work presented here is mostly focused on the assessment, implementation, and validation of the drag and lift interfacial closures. The numerical assessment and validation are performed using both analytical and industrial-like test cases for complex bubbly flows (both with wall and bulk void fraction maximums), as well as transitional flow from bubbly to slug regime using the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) experimental facility known as MT-Loop.