Type Of Instability Research Articles

Nonlinear evolution of fluting oscillations in coronal flux tubes

Magnetic flux tubes in the solar corona support a rich variety of transverse oscillations, which are theoretically interpreted as magnetohydrodynamic (MHD) modes with a fast and/or Alfvénic character. In the standard flux tube model made of a straight cylindrical tube, these modes can be classified according to their azimuthal wavenumber, m. Sausage m = 0 modes produce periodic expansion and contraction of the tube cross section and are observed during solar flares. Kink m = 1 modes laterally displace the tube axis and are related to, for example, post-flare global transverse oscillations of coronal loops. Fluting m ≥ 2 modes produce disturbances that are mainly confined to the tube boundary, but their observation remains elusive to date. We use 3D ideal MHD numerical simulations to investigate the nonlinear evolution of fluting modes in coronal flux tubes with transversely nonuniform boundaries. The simulations show that fluting modes are short-lived as coherent, collective motions of the flux tube. Owing to the process of resonant absorption, fluting oscillations become overdamped modes in tubes with wide enough nonuniform boundaries. During the nonlinear evolution, shear flows drive the Kelvin-Helmholtz instability at the tube boundary, which further disrupts the coherent fluting oscillation. For large-enough oscillation amplitudes, baroclinic instabilities of Rayleigh-Taylor type are also present at locations in the boundary where the plasma acceleration is normal to the boundary. The evolution of the instabilities drives turbulence in the flux tube, which may inhibit the resonant damping. However, the oscillations remain strongly damped even in this case. As a result of the combination of the strong damping and the induced instabilities, it is unlikely that coronal flux tubes can support fluting modes as sufficiently enduring coherent oscillations.

Intensity recognition of vortex ropes in draft tube of a prototype pump turbine using an optimized CNN-BiLSTM framework with multi-head self-attention mechanism

Swirling vortex rope in draft tube (DT) is a typical hydraulic instability of a pump turbine (PT) in the pumped storage plant (PSP). In view of the potential hazards of the vortex rope, accurate recognition of its intensity is of great significance to maintain the stable operation of the PT. Due to the limitations of shallow learning algorithms during intelligent recognition, an adaptive deep learning framework is innovatively proposed in this study. Firstly, the measured high-precision pressure fluctuation signals based on the prototype PT in a Chinese PSP that can reflect different intensities of vortex ropes in the DT are utilized as the input data. Secondly, a preliminary deep learning framework that integrates convolutional neural network (CNN), bidirectional long short-term memory (BiLSTM) and multi-head self-attention mechanism (MHSAM) is constructed. Then, the Bayesian optimization algorithm (BOA) is utilized to adaptively determine several hyperparameters of the framework. And an adaptive BOA-CNN-BiLSTM-MHSAM framework is established to recognize different intensities of vortex ropes in the DT. Finally, the recognition performance of the proposed framework is demonstrated through comparing with other deep learning frameworks. And the recognition results illustrate that the proposed BOA-CNN-BiLSTM-MHSAM framework can be utilized to effectively recognize different intensities of vortex ropes in the DT. It will be a good technical reserve to improve the intelligent level of the monitoring system of the PSP.

Kink Instability of Flux Ropes in Partially Ionized Plasmas

In the solar atmosphere, flux ropes are subject to current-driven instabilities that are crucial in driving plasma eruptions, ejections, and heating. A typical ideal magnetohydrodynamics instability developing in flux ropes is the helical kink, which twists the flux rope axis. The growth of this instability can trigger magnetic reconnection, which can explain the formation of chromospheric jets and spicules, but its development has never been investigated in a partially ionized plasma (PIP). Here, we study the kink instability in PIP to understand how it develops in the solar chromosphere, where it is affected by charge-neutral interactions. Partial ionization speeds up the onset of the nonlinear phase of the instability, as the plasma β of the isolated plasma is smaller than the total plasma β of the bulk. The distribution of the released magnetic energy changes in fully ionized plasma and PIP, with a larger increase in internal energy associated with the PIP cases. The temperature in PIP increases faster also due to heating terms from the two-fluid dynamics. PIP effects trigger kink instability on shorter time scales, which is reflected in more explosive chromospheric flux rope dynamics. These results are crucial to understanding the dynamics of small-scale chromospheric structures—minifilament eruptions—that thus far have been largely neglected but could significantly contribute to chromospheric heating and jet formation.

Non-spinning tops are stable

We consider coupled gravitational and electromagnetic perturbations of a family of five-dimensional Einstein-Maxwell solutions that describes both magnetized black strings and horizonless topological stars. We find that the odd perturbations of this background lead to a master equation with five Fuchsian singularities and compute its quasinormal mode spectrum using three independent methods: Leaver, WKB and numerical integration. Our analysis confirms that odd perturbations always decay in time, while spherically symmetric even perturbations may exhibit for certain ranges of the magnetic fluxes instabilities of Gregory-Laflamme type for black strings and of Gross-Perry-Yaffe type for topological stars. This constitutes evidence that topological stars and black strings are classically stable in a finite domain of their parameter space.

Instability of Type (II) Lawson–Osserman cones

Instability of Type (II) Lawson–Osserman cones

Instabilities and self–organization in spatiotemporal epidemic dynamics driven by nonlinearity and noise

Theoretical analysis of epidemic dynamics has attracted significant attention in the aftermath of the COVID–19 pandemic. In this article, we study dynamic instabilities in a spatiotemporal compartmental epidemic model represented by a stochastic system of coupled partial differential equations (SPDE). Saturation effects in infection spread–anchored in physical considerations–lead to strong nonlinearities in the SPDE. Our goal is to study the onset of dynamic, Turing–type instabilities, and the concomitant emergence of steady–state patterns under the interplay between three critical model parameters–the saturation parameter, the noise intensity, and the transmission rate. Employing a second–order perturbation analysis to investigate stability, we uncover both diffusion–driven and noise–induced instabilities and corresponding self–organized distinct patterns of infection spread in the steady state. We also analyze the effects of the saturation parameter and the transmission rate on the instabilities and the pattern formation. In summary, our results indicate that the nuanced interplay between the three parameters considered has a profound effect on the emergence of dynamical instabilities and therefore on pattern formation in the steady state. Moreover, due to the central role played by the Turing phenomenon in pattern formation in a variety of biological dynamic systems, the results are expected to have broader significance beyond epidemic dynamics.

Transition to oscillatory instability of lean methane–air flames in microchannels

Micro-flow reactors and porous media burners are prone to instability in the form of flame with repetitive extinction and ignition (FREI) near the region of a temperature gradient. Although significant progress has been made in this field, there is still a lack of understanding regarding the nature of such stable-to-unstable transition. Some studies reported a smooth and continuous instability transition in microchannels, interpreting this phenomenon as a supercritical bifurcation. Meanwhile, others have observed that the transition is subcritical, with rapid, stepwise evolution of the stable flame to FREI. This study aims to rigorously determine the transition character theoretically and numerically using a two-dimensional model with a precise resolution of the bifurcation parameter (flow velocity) near the critical point and gradual wall temperature ramp. The results indicate that the transition is a subcritical bifurcation with strong hysteresis. However, the amplitude of the limit cycle born in the bifurcation point could be small compared to FREI-like oscillations. Moreover, further development of the instability depends significantly on the channel width. In relatively wide channels, the stable regime transforms immediately into the extinction/ignition one with rapid growth in amplitude. In moderate channels, complex transitional dynamics were observed with an evident pulsating regime, which evolved into FREI through mixed-mode oscillations. In narrow channels, the amplitude of transitional pulsating flame becomes comparable to the fully-developed extinction/ignition cycles, and the bifurcation diagram has a continuous character with no significant jumps or discontinuities. Such qualitative variation of transition character provides a possible explanation for contradictory interpretations presented in the literature.Novelty and Significance StatementCurrently, there is no consensus about the character of transition between the stable and extinction/ignition regimes in microchannels. Some studies have reported a continuous instability transition with an evident pulsating regime, interpreting it as a supercritical bifurcation, while others have observed subcritical bifurcation with a rapid transition. The novelty of this research lies in the rigorous determination of the bifurcation type and further instability development in microchannels of different widths based on an accurate simulation of flame dynamics near the critical point with very small steps of the flow velocity variation, along with the bifurcation theory. The study contributes to understanding the instability transition nature and may explain the different interpretations of the transitional phenomenon found in the literature. The results offer valuable insights for designing micro-scale and porous media combustion devices.

Research on hump characteristics improvement of low-mid specific speed high-power centrifugal pump

Abstract The hump phenomenon is a typical hydraulic instability of centrifugal pump. The hump curve is easily found on H-Q characteristic curves of centrifugal pump at low flow conditions. Hump phenomenon causes large vibration and noise and affects the unit stability of star-up process. The impeller model with specific speed ns=100 was used an initial impeller for the high-power centrifugal pump to be developed, and the meridian flow channel keep unchanged. The impeller geometry, the blade profile, blade exit edge, wrap angle, inlet blade angle were optimized to improve hump characteristics. The 3D pump model with the initial and optimized impeller were simulated to obtain the H-Q characteristic curve. The numerical simulation results show that the inlet secondary reflux is significantly weakened, energy characteristics and hump margin of the optimized impeller are obviously improved compared with the initial impeller. The optimized impeller was also tested on the model test system to verify the hump margin. The test results demonstrate that the optimized design considerably improve the centrifugal pump’s hump margin. The results of simulations and model tests verified that impeller optimization was a suitable and efficient way to enhance the hump characteristics. The result provides design reference for long-term safe and stable operation of low-mid specific speed high-power centrifugal pump.

Return Currents in Collisionless Shocks

Collisionless shocks tend to send charged particles into the upstream, driving electric currents through the plasma. Using kinetic particle-in-cell simulations, we investigate how the background thermal plasma neutralizes such currents in the upstream of quasi-parallel non-relativistic electron–proton shocks. We observe distinct processes in different regions: the far upstream, the shock precursor, and the shock foot. In the far upstream, the current is carried by nonthermal protons, which drive electrostatic modes and produce suprathermal electrons that move toward upstream infinity. Closer to the shock (in the precursor), both the current density and the momentum flux of the beam increase, which leads to electromagnetic streaming instabilities that contribute to the thermalization of suprathermal electrons. At the shock foot, these electrons are exposed to shock-reflected protons, resulting in a two-stream type instability. We analyze these processes and the resulting heating through particle tracking and controlled simulations. In particular, we show that the instability at the shock foot can make the effective thermal speed of electrons comparable to the drift speed of the reflected protons. These findings are important for understanding both the magnetic field amplification and the processes that may lead to the injection of suprathermal electrons into diffusive shock acceleration.

Investigation of the mild surge in an axial–centrifugal compressor

The performance and structural integrity of compressors are critically impacted by aerodynamic instability. This study examines an unstable phenomenon, known as high-frequency mild surge (HFMS), in axial–centrifugal compressors through an experimental investigation and a low-order model. The results reveal that the pressure signal during HFMS is synchronized along the circumferential and streamwise directions. To elucidate the HFMS mechanism and further explore its influential law, a multi-actuator model is developed, successfully capturing the dynamic instability behavior. As the mass flow decreases, the front axial stage becomes unstable first, while the latter centrifugal stage remains stable with a negative slope near the operating point on the performance curve. The strong pressurization of the centrifugal stage maintains the stability of the entire compression system, increasing the mass flow rate. Subsequently, the pressure ratio of the latter centrifugal stage decreases with increasing mass flow, causing the front axial stage to become unstable again. The axial stage's Helmholtz frequency is consistent with the test HFMS frequency, further proving that it is a local systematic instability dominated by the axial stage. This matching feature is particularly common in combined compressors, making HFMS a typical instability phenomenon in such systems.

Abstract 7522: Association between the CNTN4 expression and responsiveness to pembrolizumab in gastric cancer

Abstract Even though numerous strategies for controlling malignant tumors have been established with immunotherapies, a solution for non-favorable responses to immunotherapy is still unclear. To address this unsolved problem, we previously suggested that a new immune checkpoint, CNTN4, is expressed on the tumor side and suppresses T cell-dependent immune activation. We further investigated the association between the clinical outcome of pembrolizumab and the expression of CNTN4 in the gastric cancer cohort using bulk RNA sequencing data to establish a clinical strategy for targeting CNTN4. We split the patients into high- or low-group based on the expression of CNTN4 and CD274 (PD-L1) with the median of those two genes and analyzed for the responses. As a result, patients who had low-CNTN4 expression and high-CD274 expression were favorable to the pembrolizumab (Objective response rate, ORR; 64.3% [9/14]). However, patients who had high-CNTN4 expression and high-CD274 expression showed unfavorable responses (ORR; 0% [0/9]. Ꭓ2 = 5.951, P = 0.002). We also figured out that non-responders (NRs, N = 33) had a relatively lower expression of CD274 (p = 0.0012) and a higher expression of CNTN4 (p = 0.0015) compared to responders (Rs, N =12). Furthermore, in CD274-high patients, NRs showed significantly higher CNTN4 expression than Rs (Fold change = 2.17. P = 0.0086). Immune-related cytokine genes, such as IFNG, GZMA, and CXCL9, were negatively correlated to CNTN4 expression (R = -0.69, P = 2 × 10−4; R = -0.52, P = 0.0108; R= -0.54, and P = 0.0077, respectively.). In addition to the cancer cells, cancer-associated fibroblast, important for immunotherapy, was deconvoluted from bulk RNA data and showed higher CNTN4 expressions in NRs than Rs (Fold change = 3.3, P = 0.002). When classifying tumor tissue based on TCGA molecular subtypes, genomically stable (GS) type and chromosomal instability (CIN) were more observed in the NRs compared to the Rs with poor prognosis. CIN and GS type patients showed higher CNTN4 and lower CD274 expression than other TCGA subtypes. We also figured out that all CNTN4-high patients were composed of CIN or GS types. Similarly, higher CNTN4 expression and lower CD274 expression were observed in CIN and GS gastric patients from the TCGA database. Moreover, overall survival (OS) and progression-free survival (PFS) were poorer in CNTN4-high patients (OS: median of CNTN4-high = 9.73 [95% CI= 4.77-NA] months, median of CNTN4-low = NA [95% CI= 9.03-NA] months, P = 0.072. Hazard ratio = 2.15 [95% CI = 0.917-5.037], P = 0.078) (PFS: median of CNTN4-high = 2.10 [95% CI= 1.33-3.97] months, median of CNTN4-low = 5.47 [95% CI= 2.80-NA] months, P = 0.0004. Hazard ratio = 3.303 [95% CI = 1.647-6.624], P = 0.0008).Together, we suggest that CNTN4 is a potential ICP candidate for gastric cancer patients unfavorable to pembrolizumab treatment. The anti-CNTN4 antibody GENA-104A16 is under the IND submission stage for clinical studies. Citation Format: Mi Young Cha, Gihyeon Kim, Changho Park, Bu-Nam Jeon, Kyung Mi Park, Hansoo Park, Chan-Young Ock. Association between the CNTN4 expression and responsiveness to pembrolizumab in gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7522.

Effects of vection type and postural instability on cybersickness

This study directly compared the novel unexpected vection hypothesis and postural instability-based explanations of cybersickness in virtual reality (VR) using head-mounted displays (HMD) for the first time within a commercial VR game. A total of 40 participants (19 males and 21 females) played an HMD-VR game (Aircar) for up to 14 min, or until their first experience of cybersickness. Based on their self-reports, 24 of these participants were classified as being ‘sick’ during the experiment, with the remainder being classified as ‘well’. Consistent with the unexpected vection hypothesis, we found that: (1) ‘sick’ participants were significantly more likely to report unexpected vection (i.e., an experience of self-motion that was different to what they had been expecting), and (2) sickness severity increased (exponentially) with the strength of any unexpected (but not expected) vection. Our results also supported the predictions of postural instability theory, finding that the onset of cybersickness was typically preceded by an increase in participants’ postural instability. However, when both sway and vection measures were combined, only unexpected vection was found to significantly predict the occurrence of sickness. These findings highlight the importance of unusual vection experiences and postural instability in understanding cybersickness. However, they suggest that developers should be able to make use of expected experiences of vection to safely enhance HMD-VR.

Large electronegativity differences between adjacent atomic sites activate and stabilize ZnIn2S4 for efficient photocatalytic overall water splitting

Photocatalytic overall water splitting into hydrogen and oxygen is desirable for long-term renewable, sustainable and clean fuel production on earth. Metal sulfides are considered as ideal hydrogen-evolved photocatalysts, but their component homogeneity and typical sulfur instability cause an inert oxygen production, which remains a huge obstacle to overall water-splitting. Here, a distortion-evoked cation-site oxygen doping of ZnIn2S4 (D-O-ZIS) creates significant electronegativity differences between adjacent atomic sites, with S1 sites being electron-rich and S2 sites being electron-deficient in the local structure of S1–S2–O sites. The strong charge redistribution character activates stable oxygen reactions at S2 sites and avoids the common issue of sulfur instability in metal sulfide photocatalysis, while S1 sites favor the adsorption/desorption of hydrogen. Consequently, an overall water-splitting reaction has been realized in D-O-ZIS with a remarkable solar-to-hydrogen conversion efficiency of 0.57%, accompanying a ~ 91% retention rate after 120 h photocatalytic test. In this work, we inspire an universal design from electronegativity differences perspective to activate and stabilize metal sulfide photocatalysts for efficient overall water-splitting.

Adaptive control of transonic buffet and buffeting flow with deep reinforcement learning

The optimal control of flow and fluid–structure interaction (FSI) systems often requires an accurate model of the controlled system. However, for strongly nonlinear systems, acquiring an accurate dynamic model is a significant challenge. In this study, we employ the deep reinforcement learning (DRL) method, which does not rely on an accurate model of the controlled system, to address the control of transonic buffet (unstable flow) and transonic buffeting (structural vibration). DRL uses a deep neural network to describe the control law and optimizes it based on data obtained from interaction between control law and flow or FSI system. This study analyzes the mechanism of transonic buffet and transonic buffeting to guide the design of control system. Aiming at the control of transonic buffet, which is an unstable flow system, the control law optimized by DRL can quickly suppress fluctuating load of buffet by taking the lift coefficient as feedback signal. For the frequency lock-in phenomenon in transonic buffeting flow, which is an unstable FSI system, we add the moment coefficient and pitching displacement to feedback signal to observe pitching vibration mode. The control law optimized by DRL can also effectively eliminate or reduce pitching vibration displacement of airfoil and buffet load. The simulation results in this study show that DRL can adapt to the control of two different dynamic modes: typical forced response and FSI instability under transonic buffet, so it has a wide application prospect in the design of control laws for complex flow or FSI systems.

Curvature effect on stabilization of cellular detonations in channel, circular arc and spherical shell geometries

The stability and propagation characteristics of gaseous detonations are numerically investigated, specifically in configurations where global front surface curvature plays a significant role. The simulations use idealized constitutive models representing a weakly unstable mixture and the simulated geometries include both two-dimensional arc and spherical shell sections with rigid walls and a straight channel geometry with compliant confinement. Depending on the inner and outer arc radius, differing levels of curvature can be imparted on the propagating wave in the two curved geometries. For thinner explosive regions, cellular type instabilities develop as the wave propagates around the arc and shell. However, as the thickness of the explosive increases and progressively greater surface curvature is imposed, laminar flow regions develop which can coexist with regions dominated by unstable cellular propagation. Here, the appearance and persistence of this laminar zone is shown to coincide with a critical level of surface curvature for both the arc and shell geometries. This critical curvature concept is also tested in the corresponding straight channel configuration with a compliant confiner, which similarly produces global surface curvature on the propagating detonation front but now as function of imposed wall divergence. Similarly, the propagation in the channel is found to stabilize when the maximum surface curvature exceeds a certain critical value that is close to the analog from the curved geometries. These results support the likely existence of a critical surface curvature mechanism or criterion that ensures the stabilization of a nominally unstable cellular detonation.

Diffusion and hydrodynamic instabilities in membrane systems with water solutions of NaCl and ethanol.

The characteristic manifestations of instability were observed in the form of voltage pulsations measured between electrodes immersed directly in solutions of membrane system chambers, in different configurations of membrane systems. The reason for this type of voltage pulsations is Rayleigh-Benard type instabilities of near-membrane layers caused by density gradients of solutions in these layers. The time of build-up of the concentration boundary layer, after which hydrodynamic instability appears is one of important parameters of these phenomena. The concentration characteristics of these times, measured for one- and two-membrane systems, are nonlinear. With increasing differences in the density of solutions on the membrane at the initial moment, the times of build-up of concentration boundary layers were reduced. In two-membrane systems containing ternary solutions (water, NaCl, ethanol), ethanol was used to control the initial differences in the density of solutions on the membrane. The times of hydrodynamic instabilities in two-membrane system were symmetrical due to the concentration of ethanol, for which the densities of solutions on both sides of the membrane were the same at the initial moment. This dependence is similar for both configurations of the membrane system and is characterized by two nonlinear curves converging to the concentration of ethanol at which, at the initial moment, the densities of the solutions in the chambers of the two-membrane system are the same. In turn, the steady-state voltages of the two-membrane system as a function of the initial concentration of ethanol in the middle chamber with the same initial NaCl concentration in the middle chamber, are a complex function depending on the membrane arrangement. These voltages are characterized by a transition in the ethanol concentration range, for which, at the initial moment, the densities of the solutions in the chambers of the two-membrane system are comparable.

Super-quadric CFD-DEM study of spout deflection behaviour of non-spherical particles in a spout fluidized bed

Non-spherical particles are commonly encountered in chemical engineering processes including fluidization processes, yet their instability phenomena still lack understanding. In this study, the spout deflection – a typical instability phenomenon of non-spherical particles in a pseudo-two-dimensional (pseudo-2D) spout fluidized bed is first studied by a super-quadric computational fluid dynamics-discrete element method (super-quadric CFD-DEM) model. The intensity of spout deflection is quantified by the spout deflection angle concept. The effect of particle shape (i.e., sphere, cubic, ellipsoid, and cylinder) on the flow in terms of flow pattern, spout deflection, pressure drop, particle orientation, and normal contact force is systematically studied and compared by the time- and frequency-domain analysis. It shows that the spout channel becomes narrower for cubic, ellipsoid and cylinder particles where the particle aspect ratio increases. With the increase of spouting gas velocity, the median value of the spout deflection angle decreases and increases for cubic and ellipsoid particles, respectively. Furthermore, the pressure drops in the vertical and horizontal directions of the cubic, ellipsoid, and cylinder particles are different from each other. At last, In the bed of cubic particles, the ordered arrangements appear close to the wall region and random arrangements occur in the other regions. This work reveals the influences of non-spherical particles on spout deflection and offers insights into practical applications through optimal operation.

Magnetic field induced instability pattern evolution in an immiscible alloy

The magnetic field induced instability patterns have been observed in an undercooled immiscible Co–Cu alloy by an in situ magnetization measurement of the supercooled alloy melt. With the increase in magnetic field intensity and gradient, the undercooled immiscible melt experienced a transition from a core-shell structure to a layered structure at a lower field intensity and then a typical normal field instability pattern with the applied higher magnetic field gradient. Due to the different magnetic response ability of the separated phases in the presence of a magnetic field gradient, the transition of the morphology was complex, and its detailed investigations can provide important insight for better understanding of the ferrofluid and the creation of functional material. Furthermore, under an appropriate field gradient condition, it can achieve the subtle transitions between the diverse morphologies in an immiscible alloy.

Phase field study on fracture behavior of crushable polymer foam

Polymer foam is a widely used material across various industries for its lightweight and exceptional energy absorption capability. Nevertheless, its porous structure and compaction properties present challenges in simulating crack initiation and propagation. The phase field method has attracted much attention for its advantages in predicting cracks. In this paper, we combine the phase field method with the “crushable foam” model and introduce the modified Drucker-Prager failure criterion to establish the phase field model of polymer foam materials. Material parameters are calibrated using experimental data from uniaxial compression, uniaxial tensile and shear punching experiments. The typical tensile, shear and compression instability fracture processes of polyurethane are then simulated using the proposed model, and the numerical results agree well with the experimental results. This indicates that the coupled phase-field crushable foam model not only exhibits the compaction properties of polymer foam materials but also accurately predicts its crack propagation under complex loading. Studying the fracture behavior of polymer foams under complex loads can enhance their engineering applications.

Diagnostic accuracy of MRI for detection of occult instability of type I anterior to posterior pelvic injuries

Type I Young and Burgess anterior posterior compression (APC) pelvic injuries have been classically managed non operatively due to theoretical integrity of sacroiliac joint ligaments (SIJL), though examination under anesthesia (EUA) has been proven occult mechanical instability in up to 50% of these injuries. We sought to determine the diagnostic accuracy of magnetic resonance (MRI) for detection of occult instability on APC-I injuries when compared to EUA.Methods: Diagnostic test study of prospectively recruited patients admitted with APC-I pelvic injuries between 2015 and 2022. All patients consented to participate in this study were subjected to MRI and EUA. The evaluators of each of these tests were blinded. On MRI evaluation, SIJL were considered compromised when unilateral injury to anterior SIJL was visualized in three or more consecutive images or in bilateral injuries, when injury to the anterior SIJL in two or more consecutive images on each side was observed. Positive EUA was considered a symphyseal diastasis over 25 mm on stress fluoroscopy. Demographic data was collected as recruited and sensitivity, specificity, accuracy, and positive and negative predictive values were calculated. Confidence interval was set at 95%. EUA was considered the gold standard in statistical analysis.Results: A total of 32 patients mean aged 36 (24–61) years were included. Mean symphyseal diastasis at admission was 17.58 (11 - 25) mm. The median time from injury to EUA was 5 (0–21) days. Positive EUA was observed on 20 patients and 25 patients presented compromised SIJL. MRI presented a sensitivity of 95% (75.13% - 99.87%), specificity of 50% (21.09% - 78.91%), positive-predictive value of 73% (60.61% to 82.93%), negative-predictive value of 87% (48.66% - 98.08%).Conclusion: Injury to SIJL on MRI presented an accuracy of 77% (58.29% - 89.64%) for the detection of occult pelvic instability on EUA.