A Simplified Framework for Modelling Viscoelastic Fluids in Discrete Multiphysics

A simplified modelling technique for modelling viscoelastic fluids is proposed from the perspective of Discrete Multiphysics. This approach, based on the concept of linear additive composition of energy potentials, aims to integrate Smooth Particle Hydrodynamics (SPH) with an equivalent elastic potential tailored for fluid flow simulations. The model was implemented using a particle-based software, explored and thoroughly validated with results from numerical experiments on three different flow conditions. The model was able to successfully capture a large extent of viscoelastic responses to external forcing, ranging from pure viscous flows to creep-dominated Bingham type of behaviour. It is concluded that, thanks to the modularity and tunable characteristics of the parameters involved, the proposed modelling approach can be a powerful simulation tool for modelling or mimicking the behaviour of viscoelastic substances.

Therapeutic niche of hyaluronic acid derivatives in osteoarthritis

Osteoarthritis (OA) is a widespread disease of synovial joints, the treatment of which determines a significant number of tactical and strategic directions. Currently, there is experience in the local use of so-called synovial fluid (SF) prostheses, which are viscoelastic substances that improve the cushioning properties of the native intra-articular environment. The overwhelming majority of viscoelastic additives are represented by hyaluronic acid (HA) derivatives, a natural component of SF, whose biological role consists in maintaining the rheological properties of fluid and the presence of anti-inflammatory, anti-nociceptive and chondro-protective properties. In the development of HA drugs, the main goals are the sustained and controlled release of therapeutic doses of the drug, taking into account the choice of carrier, drug molecule and target articular tissue. Assessing the quality and physiological feasibility of introducing a particular viscoelastic drug into the joint involves determining the so-called crossover frequency - the point of intersection of the viscosity modulus G’ and the elastic modulus G” (G’/G”), which reflects changes in the viscoelastic properties of the SF with increasing load frequency when transitioning from walking to running. Physiological range of frequencies out of the majority of investigated medical products corresponds to a single one, among which there are also variants of domestic production. Numerous studies of local application of some HA drugs in patients with OA confirm their effectiveness and safety, in particular, reduction of pain syndrome, reduction of the need for nonsteroidal anti-inflammatory drugs, improvement of the quality of life. However, unfortunately, most HA drugs available on the market have not undergone full-fledged clinical trials, so there is a need to study the comparative effectiveness of drugs of this group approved for use and determine their place in the treatment of OA with different variants of the course.