Numerical Study on the Rising Motion of Bubbles near the Wall

Based on the volume of fluid method (VOF), the rising characteristics of bubbles in near-wall static water are studied. In this study, the influence of the wall on the rising motion of the bubble was studied by changing the distance of the bubble wall, the diameter of the bubble, the arrangement of the bubble and the size ratio, etc. The influence is expressed as the average swing amplitude of the “Z”-shaped motion when the bubble rises. The study found that in the case of a single bubble, the wall surface has a certain influence on the rise of the bubble, and its degree is affected by the bubble wall distance and the bubble diameter. The influence of bubble wall distance is more obvious. The greater the bubble wall distance, the less the bubble is affected by the wall; in the case of double bubbles, the influence of the interaction force between the bubbles is significantly greater than the wall surface.

Linear-model-based estimation in wall turbulence: improved stochastic forcing and eddy viscosity terms

We use Navier–Stokes-based linear models for wall-bounded turbulent flows to estimate large-scale fluctuations at different wall-normal locations from their measurements at a single wall-normal location. In these models, we replace the nonlinear term by a combination of a stochastic forcing term and an eddy dissipation term. The stochastic forcing term plays a role in energy production by the large scales, and the eddy dissipation term plays a role in energy dissipation by the small scales. Based on the results in channel flow, we find that the models can estimate large-scale fluctuations with reasonable accuracy only when the stochastic forcing and eddy dissipation terms vary with wall distance and with the length scale of the fluctuations to be estimated. The dependence on the wall distance ensures that energy production and energy dissipation are not concentrated close to the wall but are evenly distributed across the near-wall and logarithmic regions. The dependence on the length scale of the fluctuations ensures that lower wavelength fluctuations are not excessively damped by the eddy dissipation term and hence that the dominant scales shift towards lower wavelengths towards the wall. This highlights that, on the one hand, energy extraction in wall turbulence is predominantly linear and thus physics-based linear models give reasonably accurate results. On the other hand, the absence of linearly unstable modes in wall turbulence means that the nonlinear term still plays an essential role in energy extraction and thus the modelled terms should include the observed wall distance and length scale dependencies of the nonlinear term.

Extra-skeletal manifestations in axial spondyloarthritis are associated with worse clinical outcome despite the use of TNF blocking therapy

Objective To investigate the prevalence and 4-year incidence of acute anterior uveitis (AAU), inflammatory bowel disease (IBD) and psoriasis, and to explore associations of newly developed extra-skeletal manifestations (ESMs) with clinical disease outcome in a large cohort of axial spondyloarthritis (SpA) patients. Methods All consecutive patients included in the Groningen Leeuwarden Axial SpA (GLAS) cohort between 2004 and 2011 were analysed. History of ESMs at baseline and newly developed ESMs during 4-year follow-up were only recorded when diagnosis by an ophthalmologist, gastroenterologist or dermatologist was present. Results Of the 414 included axial SpA patients, 31.5% had a positive history of one or more ESMs: 24.9% AAU, 9.4% IBD, and 4.4% psoriasis. History of psoriasis was significantly associated with more radiographic damage, especially of the cervical spine. Of the 362 patients with 4-year follow-up data, 15.7% patients developed an ESM: 13.3% patients with AAU, of which 3.6% had a first episode and 9.7% had recurrent AAU, 1.9% developed IBD, and 0.8% developed psoriasis. Patients who newly developed ESMs (without history of ESMs) had worse ASQoL score (mean 10.0 vs. 5.9, p=0.001), larger occiput to wall distance (median 6.3 vs. 2.0, p=0.021) and more limited modified Schober test (mean 12.6 vs. 13.6, p=0.014) after 4 years of follow-up. The majority of patients developing an ESM used anti-TNF therapy. Conclusion History of ESMs was present at baseline in one-third of axial SpA patients. The 4-year incidence of ESMs was relatively low, but patients who developed a new ESM reported worse quality of life.

Minimum Wall Distance Computations With Time-Dependent Geometry for CFD

This paper presents an efficient and scalable method to calculate the minimum wall distance (MWD), which is necessary for the Reynolds-Averaged Navier-Stokes (RANS) turbulence models. The MWD is described by the distance field function which is essentially a partial differential equation (PDE). The PDE is a type of convection-diffusion equation and can be solved by existing computational fluid dynamics (CFD) codes with minor modifications. Parallel computations for the PDE are conducted to study its efficiency and scalability. Encouraging results are obtained and demonstrate the present method is more efficient than all the alternate methods.

Contribution of Particle–Wall Distance and Rotational Motion of a Single Confined Elliptical Particle to the Effective Viscosity in Pressure-Driven Plane Poiseuille Flows

Rheological properties of the suspension flow, especially effective viscosity, partly depend on spatial arrangement and motion of suspended particles. It is important to consider effective viscosity from the microscopic point of view. For elliptical particles, the equilibrium position of inertial migration in confined state is unclear, and there are few studies on the relationship between dynamics of suspended particles and induced local effective viscosity distribution. Contribution of a single circular or elliptical particle flowing between parallel plates to the effective viscosity was studied, focusing on the particle–wall distance and particle rotational motion using the two-dimensional regularized lattice Boltzmann method and virtual flux method. As a result, confinement effects of the elliptical particle on the equilibrium position of inertial migration were summarized using three definitions of confinement. In addition, the effects of particle shape (aspect ratio and confinement) on the effective viscosity were assessed focusing on the particle–wall distance. The contribution of particle shape to the effective viscosity was found to be enhanced when the particle flowed near the wall. Focusing on the spatial and temporal variation of relative viscosity evaluated from wall shear stress, it was found that the spatial variation of the local relative viscosity was larger than temporal variation regardless of the aspect ratio and particle–wall distance.

POS0239 ROOT JOINT INVOLVEMENT IN SPONDYLOARTHRITIS: A POST-HOC ANALYSIS FROM THE INTERNATIONAL ASAS-PERSPA STUDY

Background:In patients with spondyloarthritis (SpA), root joint diseases (RJD), i.e. hip or shoulder involvement, may be associated with a distinct disease phenotype compared to those with other affected joints. The ASAS-PerSpA study (PERipheral involvement in SPondyloArthritis) [1], offers a unique opportunity to study the phenotypes of patients with RJD in a global cohort.Objectives:Primary objective was to compare the clinical characteristics of SpA patients with and without RJD. Secondary objectives were to compare the prevalence of RJD across the different SpA subtypes and the different regions of the world, compare the severity of axial disease as well as the disease burden in SpA patients with and without RJD.Methods:This is a post-hoc analysis of the ASAS-PerSpA study, which included 4,465 patients with any subtype of SpA (axial SpA (axSpA), peripheral SpA (pSpA), psoriatic arthritis (PsA), inflammatory bowel disease associated SpA (IBD-SpA), reactive arthritis (ReA) and Juvenile SpA (Juv-SpA)) according to the rheumatologist’s diagnosis. RJD was defined as a positive answer by the investigator to the following question: “Do you consider that the patient has ever suffered from RJD (e.g. hip, shoulder) related to SpA?” In case of a positive answer, a potential specific treatment (e.g. Total Articular Replacement) was investigated. The patient’s characteristics were compared between those with and without RJD involvement, using Chi-2 or Fisher exact test for the categorical variables and t-test for the continuous variables. Two separate multivariable stepwise binary logistic regression analyses were conducted to identify factors associated with the dependent variables “hip involvement” and “shoulder involvement”.Results:RJD occurred in 1,503 patients (33.7%), with more prevalent hip (24.2%) than shoulder (13.2%) involvement. The prevalence of RJD as a group was the highest in Juv-SpA (52.7%), followed by pSpA (44.3%) and axSpA (33.9%). The highest prevalence of RJD was found in Asia and the lowest in Europe and North America. Among patients with hip involvement, 6.0% had a history of hip replacement (highest in the Middle East and North Africa and Latin America); among patients with shoulder involvement, 0.8% had a history of shoulder replacement. Hip had a distinct pattern of associations compared to shoulder involvement (Figure 1). Hip involvement was significantly associated with the SpA main diagnosis (highest in pSpA, lowest in PsA), younger age at first SpA symptom, lower prevalence of family history of psoriasis, positive HLA-B27, occiput-to-wall distance>0, and treatment with cs-DMARDs and b-DMARDs. Shoulder involvement was associated with the SpA main diagnosis (highest in Juv-SpA and pSpA, lowest in axSpA), older age at first SpA symptom, higher prevalence of enthesitis, dactylitis, tender joints count, IBD, occiput-to-wall distance>0, EQ5D score and treatment with cs-DMARDs.Conclusion:Hip involvement was more prevalent than shoulder involvement in patients with SpA, and had a distinct phenotype resembling axial disease whereas shoulder involvement was mostly associated with features of peripheral disease. Hip and shoulder involvement should be analyzed separately in future studies rather than under the RJD entity.References:[1]Lopez-medina, C. et al. Prevalence and Distribution of Peripheral Musculoskeletal Manifestations in Axial Spondyloarthritis, Peripheral Spondyloarthritis and Psoriatic Arthritis: Results of the International, Cross-sectional ASAS-PerSpA Study. RMD Open; 2021;7:e001450.Disclosure of Interests:None declared