Shear Rate Research Articles

Shear rate and roughness effect on clay-steel interface strength properties in CU and CPD drainage conditions

Based on the concept of the preformed failure plane, this paper conducted a series of clay-interface tests using a modified triaxial apparatus that can directly measure the interface pore pressure, to investigate the shear rate and interface roughness effect on the deviator stress, interface excess pore pressure, interface stress path, and interface friction angle in both consolidated undrained (CU) and consolidated partially drained (CPD) interface drainage conditions. In general, the specimen with the clay-steel interface had a lower shear strength than the pure clay specimen under the same testing conditions. In CU tests, the total and effective interface friction angles increase approximately linearly with the shear rate in the semi-logarithmic scale, while in CPD tests, both the total and effective interface friction angles decrease with increasing shear rate. Moreover, the increased surface roughness is found to enhance the interface shear strength and the maximum interface pore pressure at a given shear rate and confining pressure. In CU tests, both the normalized efficiency parameter E and the corresponding interface friction angle increase with the average roughness (Ra) in a logarithmic relationship, but it is difficult to describe the positive correlation perfectly in CPD tests.

Thompson and Troian slip effects on ternary hybrid nanofluid flow over a permeable plate with chemical reaction

This study seeks to elucidate the electromagnetic hydro-thermal aspects of ternary hybrid nanofluid (THNF) (MoS2-SiO2-GO/water) flow over a permeable plate in the presence of Thomson and Troian slip, suction/blowing, and chemical reaction. Through the utilization of similarity transformations, the nonlinear partial differential equations (PDEs) representing the conservation of mass, momentum, energy, and concentration, are converted into ordinary differential equations (ODEs). The subsequent step involves solving these ODEs utilizing the bvp4c technique in MATLAB. The detailed graphical representations precisely elucidate the action of diverse parameters, such as Hartmann number, electric parameter, velocity slip parameter, Lewis number, critical shear rate, suction/blowing, thermophoresis, and Brownian motion parameter on the velocity, thermal, and concentration profiles. The momentum and temperature distributions respond oppositely to the parameters Hartmann number, electric parameter, and suction/blowing. Also, the absolute values of Nusselt and Sherwood numbers increase with elevated critical shear rate, velocity slip, and suction/blowing parameter but decrease with higher Lewis number and chemical reaction parameter. Moreover, adjusting the velocity slip parameter from 0.2 to 0.6 results in a 24.14% decrease in the skin friction coefficient and a 16.79% increase in the local Nusselt number.

Continuous Anode Slurry Production in Twin-Screw Extruders: Effects of the Process Setup on the Dispersion

Screw design in the extrusion process has an important effect on the distribution of material through the extruder, resulting in partially filled sections in the processing zone. Accordingly, the local accumulation of material in the extruder leads to variations in material strain conditions and also influences the local residence time of the material in a given screw section. This work evaluates particle dispersion in anode slurry considering three different screw arrangements. The particle size distribution is considered as a quality parameter representing the microstructure of the battery slurry components and their distribution. Numerical simulation of the material flow behavior through a laboratory extruder was performed to investigate the filling ratios and resulting shear rates for different screw designs and process conditions. The importance of process parameters and a suitable screw configuration to achieve specific particle sizes in battery slurry is discussed.

Molecular dynamics study of the rheology of benzene-based nanofluids with metal particles

The purpose of this paper is to study the rheology of the nanofluids with ordinary spherical particles. The rheology of benzene and benzene-based nanofluids with copper and aluminium particles of 3 and 6 nm diameter been studied by the nonequilibrium molecular dynamics method. The maximum volume concentration of the nanoparticles was 6.11 %. It has been shown that all fluids considered, including benzene and benzene-based nanofluids, exhibit Newtonian behavior at low shear rates. However, with increasing shear rate, both benzene and nanofluids become pseudoplastic. The mechanisms of the rheology change of simple liquid and nanofluids have studied. This change in their rheology is a threshold phenomenon, in which the critical shear rate depends on the concentration, size, and material of the nanoparticles. The critical shear rate increases with increasing particle size and decreases with increasing particle concentration. Correlations describing the critical shear rates at which the rheology of nanofluids changes are obtained. It is shown that the rheology change is due to a change in the structure of both the base fluid and the nanofluid. In all cases, the change in rheology results from the weakening of the short-range order in these fluids. As the shear rate increases, the difference between viscosity of the base fluid and all studied nanofluids decreases monotonically.

Elasto-inertial instability in torsional flows of shear-thinning viscoelastic fluids

It is well known that inertia-free shearing flows of a viscoelastic fluid with curved streamlines, such as the torsional flow between a rotating cone and plate or the flow in a Taylor–Couette geometry, can become unstable to a three-dimensional time-dependent instability at conditions exceeding a critical Weissenberg ( $Wi$ ) number. However, the combined effects of fluid elasticity, shear thinning and finite inertia (as quantified by the Reynolds number $Re$ ) on the onset of elasto-inertial instabilities are not fully understood. Using a set of cone–plate geometries, we experimentally explore the entire $Wi$ – $Re$ phase space for a series of nonlinear viscoelastic fluids (with the dependence on shear rate $\dot{\gamma}$ quantified using a shear-thinning parameter $\beta _P(\dot {\gamma })$ ). We tune $\beta _P(\dot {\gamma })$ by varying the dissolved polymer concentration in solution. This progressively reduces shear thinning but leads to finite inertial effects before the onset of elastic instability, and thus naturally results in elasto-inertial coupling. Time-resolved rheometric measurements and flow visualization experiments allow us to investigate the effects of flow geometry, and document the combined effects of varying $Wi, Re$ and $\beta _P(\dot {\gamma })$ on the emergence of secondary motions at the onset of instability. The resulting critical state diagram quantitatively depicts the competition between the stabilizing effects of shear thinning and the destabilizing effects of inertia. We extend the curved streamline instability criterion of Pakdel & McKinley (Phys. Rev. Lett., vol. 77, no. 12, 1996, p. 2459) for the onset of purely elastic instability in curvilinear geometries by using scaling arguments to incorporate shear thinning and finite inertial effects. The augmented condition facilitates predictions of the onset of instability over a broader range of flow conditions, and thus bridges the gap between purely elastic and elasto-inertial curved streamline instabilities.

A fractal approach to ocean Ekman transport

This work examines ocean Ekman current dynamics in fractal dimensions based on the concept of product-like fractal measure introduced recently by Li and Ostoja-Starzewski in their formulation of anisotropic continuum media. We show that fractal dimensions of the fluid affects the amplitude and the shape of the velocity profile. It was observed that fast-moving current occurs for fractal dimensions much less than unity whereas slow-moving current arises for fractal dimensions close to unity. A large flow velocity leads to a decrease in the shear rate and an increase in the viscosity, a fact that has been observed in physical oceanography.

Dysphagia food: Impact of soy protein isolate (SPI) addition on textural, physicochemical and microstructural properties of peach complex gels

In this study, dysphagia-friendly diets were prepared based on the interaction between polysaccharides from peach, namely Meirui (MR), Yangshan (YS) and Cons758 (Cons), and soy protein isolate (SPI). MR-alcohol insoluble residues (AIR) and YS-AIR were low methoxylated polymers, while Cons-AIR was high methoxylated polymer. According to the international dysphagia diet standardization initiative, YS-SPI and MR-SPI could be qualified as level 5-minced/moist dysphagia diets. Following SPI addition, the apparent viscosity, G′ and G″ of peach pulp-SPI complexes were significantly increased. At the shear rate of 10 s−1, corresponding to oral processing, MR-SPI performed the highest apparent viscosity (35.2 Pa s), followed by YS-SPI (33.5 Pa s). Additionally, the SPI-treated strategy pronounced improved the hardness, springiness, adhesiveness and chewiness of complexes. Both YS-SPI and Cons-SPI showed the reduced particle size, alongside the uniform distribution, owing to the strong hydrogen bonding and electrostatic interaction between peach pulp substances and SPI, which was confirmed by FT-IR result. The biggest ζ-potential value (−23.55 mV) was found in YS-SPI. Meanwhile, compared with peach pulps, the highest increase ratio (87.94%) of water holding capacity was depicted in MR-SPI. LF-NMR analysis revealed immobilized water was dominant in peach pulp-SPI. The results suggested that MR was promising for the optimal choice to form gel food for people with swallowing problems.

An engineering approach to the 3D printing of K‐Carrageenan/konjac glucomannan hydrogels

SummaryAqueous solutions of Konjac glucomannan (KGM)/κ‐Carrageenan (κ‐C) of different ratios (1:2, 1:5, 1:8 and 1:10) and a fixed κ‐C content of 1.5%, were proposed as a new 3D food printing ink. Their thermo‐responsive behaviour was evaluated by temperature ramp rheological tests. This characterisation allowed for the evaluation of the synergistic effect between KGM and κ‐C and gave indications useful to the printing performance. Both elastic (G′) and loss (G″) moduli were found to increase by increasing the KGM concentration. Samples were printed by controlling the thermally reversible sol/gel transition occurring during the process. Direct pressure and flow rate measurements in the 3D printer were used to obtain the viscosity versus shear rate curves under processing conditions, useful to validate a scaling law relating the printing filament diameter to the relevant process and material properties (inks viscosity and printing pressure). The 3D printing performance of inks was evaluated by means of a novel, integrated score system. The results obtained indicate that aqueous mixtures of KGM/κ‐C can be successfully employed as a base for 3D printing food hydrogels. The use of the score system above outlined proved to be an easy yet efficient tool for the optimisation of the gel composition.

Experimental Study of Direct Shear Properties of Anisotropic Reservoir Shale

Understanding the shear mechanical properties of shale reservoirs is of great significance in the study of the formation stability around horizontal shale wells and the propagation and evolution of fractures for shale fracturing. However, the existing direct shear test results are limited due to small sample sizes and low shear rates. Based on previous experimental research results, the mechanical properties of anisotropic reservoir shale in direct shear tests with different experimental conditions were explored in this study. It was found that the shear mode, shear strain rate, and normal stress have a significant impact on the deformation and failure characteristics of shale. The peak shear displacement, peak shear strength, and shear stiffness of shale present an increasing trend of fluctuation, with an increase in the bedding angle. The peak shear strength of shale decreases with an increase in the shear strain rate, and this decrease trend descends with an increase in the shear strain rate. The shape of the shear fracture zone and the shear fracture mode of shale exhibit bedding effect characteristics. The fractal dimension of the shale shear fracture surface morphology shows a trend of fluctuation with the variation in the bedding angle. Further, the shear strain rate was found to play a dominant role in the fractal dimension of the shear fracture surface. The larger shear strain rate strengthens the bedding effect of the roughness for the shear fracture surface morphology. The results of this study provide a theoretical reference for determining the engineering geomechanics characteristics of shale reservoirs.

Rheological and tribological properties of seaweed powders as thickeners for liquid foods

Thickened liquid foods are particularly interesting in culinary applications and the management of swallowing disorders. Polysaccharide molecules and suspended soft particles play a major role in increasing viscosity and mouthfeel. In this work, tribo-rheological effects of finely ground particles (less than 75 μm) of Durvillaea antarctica seaweed (SP) as a minimally processed and natural alternative to commercial thickeners were studied. Shear viscosity (η), viscoelastic moduli (G′, G″), and the coefficient of friction (CoF) were determined for SP dispersions, using as controls two commercial thickeners: modified maize starch-based (TE) and xanthan gum-based (TU). SP and SP dispersions were characterized microstructurally and evaluated at concentrations of 1.2%, 2.4%, and 4.8% w/v, with and without artificial saliva (AS). SP dispersions exhibited a pseudoplastic behavior in the range of shear rates 0.1–100 s−1 and viscoelasticity (G’>G”) in the 0.1–80 rad/s frequency range. The incorporation of AS had a dilution effect in SP and TU dispersions, but additionally, in the case of TE, a hydrolyzing effect decreased the values of the responses. In the tribology experiments, all samples followed a Stribeck curve. SP dispersions were more lubricating than AS and controls in the physiological range of velocities during oral processing and swallowing (e.g.,>100 mm/s). The thickening, viscoelastic, and lubrication behavior of SP dispersions were attributed to the soluble solids released from the SP (37%–51% d. w.) and interactions with ghosts of SP particles in the continuous aqueous phase. Fine seaweed particles may be a sustainable and low-cost alternative to commercial thickeners in some food applications.

A simplified drop breakage model for emulsion-producing fluidic devices: Application to fluidic oscillator, helical coil and vortex-based cavitation device

Droplet size distribution (DSD) is one of the key quality attributes of liquid–liquid emulsions. Various fluidic devices are used to generate emulsions. Most of the currently available models for estimating DSD are complicated to implement and computationally expensive. In this work, we have developed a simplified drop breakage model that is easy to implement and computationally inexpensive. This model approximates DSDs in three droplet populations, each characterised by a mean diameter. The developed drop breakage model was applied to simulate Sauter mean diameters of oil-in-water emulsions generated using three fluidic devices covering a broad range of shear rates and droplet sizes namely: vortex-based cavitation device (VD), helical coil (HC), and fluidic oscillator (FO). The variation of DSD with the number of passes (np) through the emulsion-producing fluidic devices was measured experimentally. The Sauter mean diameter (d32) and number of droplets (n) in each population were estimated from the measured DSD data. The procedure to estimate model parameters is presented. The simplified breakage model presented here was able to simulate the influence of the number of passes and operating conditions on Sauter mean diameter as well as breakage efficiency. VD was found to exhibit the highest drop breakage efficiency. FO was found to be a preferred choice for low (< 20 J/kg) energy consumption, HC for the middle range (20 – 100 J/kg) and VD for the higher (> 100 J/kg) range of energy consumption. The developed approach and model provide a simplified way of simulating the Sauter mean diameters of emulsions for a variety of emulsion-generating devices.

Rheology of magnetorheological shear thickening polishing fluids with micro diamond abrasive particles

Magnetorheological shear thickening polishing (MRSTP) has the dual effect of shear thickening and magnetization enhancement, thereby enhancing polishing efficiency. MRSTP fluids (MRSTPFs) were prepared using polyethylene glycol (PEG), silicon dioxide (SiO2), carbonyl iron particles (CIPs), and diamond micro-abrasive particles. MRSTPFs containing diamond particles of various sizes were prepared for rheological tests. A rheological hypothesis was proposed regarding the development of CIPs chains and the ability to aggregate PEG and SiO2. Rheological tests results indicated that each sample exhibited shear thickening and magnetization enhancement effects under the magnetic field and shear rate. The shear thickening effect decreased with increasing magnetic flux density, while the overall viscosity and shear stress increased. As the magnetic flux density increased from 0 mT to 112 mT, the thickening ratio of MRSTPFs containing 3 μm diamond particles decreased from 18.94 to 1.37, but the peak viscosity increased from 5.208 Pa·s to 3639 Pa·s. The thickening ratios of MRSTPFs with different abrasive sizes showed a slight variation from 0.11 to 1.76 at the same magnetic flux density of 22 mT, 45 mT, 68 mT, 90 mT, and 112 mT, respectively. It demonstrated that the diamond particle size did not have a significant effect on the rheological properties of MRSTPFs. The correctness of the hypothesis was confirmed. The storage modulus of MRSTPFs exceeded the loss modulus at non-zero magnetic flux density, indicating that the MRSTPFs had become semi-solid. The microscopic mechanism showed that the rheological characteristics were determined by the evolution of the chain structure of CIPs and the binding ability of PEG to SiO2. This study provided valuable insights into exploring mechanisms of MRSTPFs and demonstrating the potential application of MRSTP.

Tracking Fibrinolysis of Chandler Loop-Formed Whole Blood Clots Under Shear Flow in An In-Vitro Thrombolysis Model.

Thromboembolism and related complications are a leading cause of morbidity and mortality worldwide and various assays have been developed to test thrombolytic drug efficiency both in vitro and in vivo. There is increasing demand for more physiologically relevant in-vitro clot models for drug development due to the complexity and cost associated with animal models in addition to their often lack of translatability to human physiology. Flow, pressure, and shear rate are important characteristics of the circulatory system, with clots that are formed under flow displaying different morphology and digestion characteristics than statically formed clots. These factors are often unrepresented in conventional in-vitro clot digestion assays, which can have pharmacological implications that impact drug translational success rates. The Real-Time Fluorometric Flowing Fibrinolysis (RT-FluFF) assay was developed as a high-fidelity thrombolysis testing platform that uses fluorescently tagged clots formed under shear flow, which are then digested using circulating plasma in the presence or absence of fibrinolytic pharmaceutical agents. Modifying the flow rates of both clot formation and clot digestion steps allows the system to imitate arterial, pulmonary, and venous conditions across highly diverse experimental setups. Measurements can be taken continuously using an in-line fluorometer or by taking discrete time points, as well as a conventional end point clot mass measurement. The RT-FluFF assay is a flexible system that allows for the real-time tracking of clot digestion under flow conditions that more accurately represent in-vivo physiological conditions while retaining the control and reproducibility of an in-vitro testing system.

Thermal performance of a motile-microorganism within the two-phase nanofluid flow for the distinct non-Newtonian models on static and moving surfaces

Nanofluid plays a crucial role in addressing the heat transmission challenges facing the industries including chemical processing systems, automobile radiators, spacecraft design, concrete heating, solar thermal conversion systems, etc. Consequently, this research is devoted to analyzing the solar radiation mechanism, thermophoresis and Brownian motion under unique conditions, specifically, temperature gradient within liquids with limiting viscosities or plastic dynamic viscosity at zero and infinite shear rate. To increase the model novelty, a model involving two phases of Casson–Carreau fluid conveying tiny particles is developed to analyze the flow of solar radiation mechanism over stationary and moving surfaces. Furthermore, the impacts of heat generation, chemical reaction and activation energy are also taken into account. The dimensionless equations are solved through numerical methods using the Galerkin-weighted residual technique and analytically employing the Homotopy analysis method with the assistance of MATHMATIACA 11.3 software. Our study reveals that the fluid temperature reduces for greater values of Weissenberg number, and Casson parameter. Additionally, the distribution of gyrotactic microorganisms decreased against the bio-convective Schmidt number and Peclet number.

The impact of small movements with dual lumen cannulae during venovenous extracorporeal membrane oxygenation: A computational fluid dynamics analysis

Background and objectivesVenovenous Extracorporeal Membrane Oxygenation (VV ECMO) provides respiratory support to patients with severe lung disease failing conventional medical therapy. An essential component of the ECMO circuit are the cannulas, which drain and return blood into the body. Despite being anchored to the patient to prevent accidental removal, minor cannula movements are common during ECMO. The clinical and haemodynamic consequences of these small movements are currently unclear. This study investigated the risk of thrombosis and recirculation caused by small movements of a dual lumen cannula (DLC) in an adult using computational fluid dynamics. MethodsThe 3D model of an AVALON Elite DLC (27 Fr) and a patient-specific vena cava and right atrium were generated for an adult patient on ECMO. The baseline cannula position was generated where the return jet enters the tricuspid valve. Alternative cannula positions were obtained by shifting the cannula 5 and 15 mm towards inferior (IVC) and superior (SVC) vena cava, respectively. ECMO settings of 4 L/min blood flow and pulsatile flow at SVC and IVC were applied. Recirculation was defined as a scalar value indicating the infused oxygenated blood inside the drainage lumen, while thrombosis risk was evaluated by shear stress, stagnation volume, washout, and turbulent kinetic energy. ResultsRecirculation for all models was less than 3.1 %. DLC movements between -5 to 15 mm increased shear stress and turbulence kinetic energy up to 24.7 % and 11.8 %, respectively, compared to the baseline cannula position leading to a higher predicted thrombosis risk. All models obtained a complete washout after nine seconds except for when the cannula migrated 15 mm into the SVC, indicating persisting stasis and circulating zones. ConclusionIn conclusion, small DLC movements were not associated with an increased risk of recirculation. However, they may increase the risk of thrombosis due to increased shear rate, turbulence, and slower washout of blood. Developing effective cannula securement devices may reduce this risk.

Field-induced magnetorheological study towards the active magneto-viscoelastic behavior of stable MnFe2O4 magnetic nanofluid

This work presents the fine-tuned synthesis of MnFe2O4 oleic acid-coated magnetic nanoparticles (MNPs) by the chemical co-precipitation method. The X-ray photoelectron spectroscopy (XPS) was utilized to investigate the elemental composition and oxidation state of oleic acid-coated MnFe2O4 MNPs. The Fourier transform infrared spectroscopy (FTIR) spectra were used to confirm the functional groups in the oleic acid-coated MnFe2O4 magnetic nanoparticles. The spherical shape of MnFe2O4 MNPs is confirmed by Field emission scanning electron microscopy (FESEM) and High-resolution transmission electron microscopy (HRTEM) techniques. Zeta potential (ζ) measurements were performed to confirm the stability of MnFe2O4 magnetic nanofluid (MNF). Magnetic measurements (M−vs−H) reveal the saturation magnetization, Ms = 20.3 emu/g and coercivity, HC = 30 Oe, confirming the single domain superparamagnetic nature at 300 K. Field-induced shear thinning behavior of the MnFe2O4 magnetic fluid is confirmed by a power law, η = c γn + n∞ and steady-state behavior measurements. Magneto viscous effect initially increased at a low shear rate of 20 s−1 and then decreased at a higher shear rate of 100 s−1, which confirms the stability of the MnFe2O4 magnetic fluid. Also, the highest deflection angle, θ = 243 m.rad of MnFe2O4 magnetic fluid was observed at a moderate shear rate 100 s−1 and a high magnetic field of 1.2 T, while the lowest value of deflection angle, θ = 65 m.rad was observed in the absence of magnetic field. In contrast, the storage modulus (G') is greater than the loss modulus (G''), in corroboration with the viscoelastic-to-viscous behavior of MnFe2O4 magnetic fluid.

Analytical solution of the Poiseuille flow of a De Kee viscoplastic fluid

We provide an explicit analytical solution of the planar Poiseuille flow of a viscoplastic fluid governed by the constitutive equation proposed by De Kee and Turcotte (1980). Formulae for the velocity and the flow rate are derived, making use of the Lambert W function. It is shown that a solution does not always exist because the flow curve is bounded from above and hence the rheological model can accommodate stresses only up to a certain limit. In fact, the flow curve reaches a peak at a critical shear rate, beyond which it exhibits a negative slope, giving rise to unstable solutions.

Vibrorheology of fresh cement-based materials with different compaction energy

Vibration is commonly applied to the placement of cement-based materials to improve their fluidity and compactness. Appropriate compaction could ensure the designed performance by preventing the formation of voids and cavities within a structure. In recent years, the application of vibration has been extended to the rheology control of 3D printable concrete as well. While previous studies have reported on the effective radius of compaction and rheological changes in cement-based materials induced by poker-type vibrators, there has been limited in-depth research on the rheological behavior beyond this effective radius, particularly in relation to the compaction energy. This study investigates the rheological behavior of a cement-based material under controlled vibration energy across a wide range of shear rates. A novel device is proposed for the precise control of compaction energy, in terms of the energy transfer rate per unit volume (power density) of vibration, and the vibrorheology under various power densities is measured. Experimental results reveal that viscosity at a low shear rate decreases proportionally to power density, while vibration has negligible effects on viscosity at a high shear rate. Furthermore, a correlation between power density and normalized yield stress is established, along with the effects of varying water-to-cement ratios. The study also discusses the influence of the vibration frequency on the effective radius of the poker-type vibrator.

The structure of turbulence in unsteady flow over urban canopies

The topology of turbulent coherent structures is known to regulate the transport of energy, mass and momentum in the atmospheric boundary layer (ABL). While previous research has primarily focused on characterizing the structure of turbulence in stationary ABL flows, real-world scenarios frequently deviate from stationarity, giving rise to nuanced and poorly understood changes in the turbulence geometry and associated transport mechanisms. This study sheds light on this problem by examining topological changes in ABL turbulence induced by non-stationarity and their effects on momentum transport. Results from a large-eddy simulation of pulsatile open channel flow over an array of surface-mounted cuboids are examined. The analysis reveals that the flow pulsation triggers a phase-dependent shear rate, and the ejection-sweep pattern varies with the shear rate during the pulsatile cycle. From a turbulence structure perspective, it is attributed to the changes in the geometry of hairpin vortices. An increase (decrease) in the shear rate intensifies (relaxes) these structures, leading to an increase (decrease) in the frequency of ejections and an amplification (reduction) of their percentage contribution to the total momentum flux. Furthermore, the size of the hairpin packets undergoes variations, which depend on the geometry of the constituting hairpin vortices, yet the packet inclination preserves its orientation throughout the pulsatile cycle. These observations reinforce the important role non-stationarity holds in shaping the structure of ABL turbulence and the momentum transport mechanisms it governs.

Apolipoprotein A-IV polymorphisms Q360H and T347S attenuate its endogenous inhibition of thrombosis

Platelets are small anucleate cells that play a key role in thrombosis and hemostasis. Our group previously identified apolipoprotein A-IV (apoA-IV) as an endogenous inhibitor of thrombosis by competitive blockade of the αIIbβ3 integrin on platelets. ApoA-IV inhibition of platelets was dependent on the N-terminal D5/D13 residues, and enhanced with absence of the C-terminus, suggesting it sterically hinders its N-terminal platelet binding site. The C-terminus is also the site of common apoA-IV polymorphisms apoA-IV-1a (T347S) and apoA-IV-2 (Q360H). Interestingly, both are linked with an increased risk of cardiovascular disease, however, the underlying mechanism remains unclear. Here, we generated recombinant apoA-IV and found that the Q360H or T347S polymorphisms dampened its inhibition of platelet aggregation in human platelet-rich plasma and gel-filtered platelets, reduced its inhibition of platelet spreading, and its inhibition of P-selectin on activated platelets. Using an ex vivo thrombosis assay, we found that Q360H and T347S attenuated its inhibition of thrombosis at both high (1800s−1) and low (300s−1) shear rates. We then demonstrate a conserved monomer-dimer distribution among apoA-IV WT, Q360H, and T347S and use protein structure modelling software to show Q360H and T347S enhance C-terminal steric hindrance over the N-terminal platelet-binding site. These data provide critical insight into increased cardiovascular risk for individuals with Q360H or T347S polymorphisms.