Steady-state Method Research Articles

Flow characterization of low sweep MULDICON wing at low speed

PurposeThe flow topology for multi-disciplinary configuration (MULDICON) wing is very complicated and nonlinear at low to high angle of attack (AOA). This paper aims to provide the correlation between the unsteadiness and uncertainties of the flow topology and aerodynamic forces and moments above MULDICON WING at a medium to a higher AOA.Design/methodology/approachThe experimental and computational fluid dynamics methods were used to investigate a generic MULDICON wing. During the experiment, the AOA were varied from α = 5° to 30°, whereas yaw angle varies between β = ±20° and Reynolds number between Re = 3.0 × 105 and Re = 4.50 × 105. During the experiments steady-state loading, dynamic loading and flow visualization wind tunnel methods were used.FindingsThe standard deviation quantified the unsteadiness and uncertainties of flow topology and predicted that they significantly affect the pitching moment (Cm) at medium to higher AOA. A strong correlation between flow topology and Cm was exhibited, and the experiment data was well validated by previous numerical work. The aerodynamic center was not fixed and shifted toward the wing apex when AOA is increasing. For a = 10°, the flow becomes more asymmetric. Power spectral densities plots quantify the flow separation (apex vortex, leading-edge vortex and vortex breakdown) over the MULDICON wing.Originality/valueThe application and comparison of steady-state and dynamic loading data to quantify the unsteadiness and uncertainties of flow topology above the MULDICON wing.

Physicochemical Analysis of Chloride Diffusion and Adsorption in Water-saturated Concrete: Theory and Measurement

The theory of ionic diffusion in water-saturated concrete accompanying ion exchange with mobile or immobile adsorbed ions was constructed by using the general theory of diffusion and the condition of electrical neutrality. Analysis of the diffusion profile of chloride (Cl−) ions in concrete with the theory revealed that adsorbed Cl− ions in AFm and C-S-H are as mobile as free Cl− ions in the pore solution, so that the adsorption does not retard the ingress of Cl− ions. The existing test methods for determining the effective or apparent diffusion coefficient of Cl− ions were evaluated on the bases of the present theory and new experimental findings. It was revealed that steady-state electrochemical methods such as NTBUILD-355 and ASTM C1202 are not suitable for determining the diffusion coefficient, because the steady state methods expel preexisting diffusible ions which strongly affect the diffusion of Cl− ions. Moreover, the steady state methods overestimate the diffusion rate because the methods assume that adsorbed Cl− ions are immobile. The electrochemically-accelerated method NT BUILD 443 is also unsuitable for the diffusion test, because the acceleration is induced by the electro-osmotic flow of the external solution into concrete. The present diffusion theory necessitates the effective self-diffusion coefficient of not only Cl− ions but also all the other diffusible ions in concrete. A simple method of determining the effective self-diffusion coefficients of arbitrary ions in concrete from the diffusion profile of Cl− ions was presented.

A robust luminescent assay for screening alkyladenine DNA glycosylase inhibitors to overcome DNA repair and temozolomide drug resistance

Temozolomide (TMZ) is an anticancer agent used to treat glioblastoma, typically following radiation therapy and/or surgical resection. However, despite its effectiveness, at least 50% of patients do not respond to TMZ, which is associated with repair and/or tolerance of TMZ-induced DNA lesions. Studies have demonstrated that alkyladenine DNA glycosylase (AAG), an enzyme that triggers the base excision repair (BER) pathway by excising TMZ-induced N3-methyladenine (3meA) and N7-methylguanine lesions, is overexpressed in glioblastoma tissues compared to normal tissues. Therefore, it is essential to develop a rapid and efficient screening method for AAG inhibitors to overcome TMZ resistance in glioblastomas. Herein, we report a robust time-resolved photoluminescence platform for identifying AAG inhibitors with improved sensitivity compared to conventional steady-state spectroscopic methods. As a proof-of-concept, this assay was used to screen 1440 food and drug administration-approved drugs against AAG, resulting in the repurposing of sunitinib as a potential AAG inhibitor. Sunitinib restored glioblastoma (GBM) cancer cell sensitivity to TMZ, inhibited GBM cell proliferation and stem cell characteristics, and induced GBM cell cycle arrest. Overall, this strategy offers a new method for the rapid identification of small-molecule inhibitors of BER enzyme activities that can prevent false negatives due to a fluorescent background.

Performance Evaluation of Novel Concentrating Photovoltaic Thermal Solar Collector under Quasi-Dynamic Conditions

Concentrating Photovoltaic Thermal (CPVT) collectors are suitable for integration in limited roof space due to their higher solar conversion efficiency. Solar sunlight can be used more effectively by CPVT collectors in comparison to individual solar thermal collectors or PV modules. In this study, the experimental investigation of a novel CPVT collector called a PC (power collector) has been carried out in real outdoor conditions, and the test set-up has been designed based on ISO 9806:2013. A quasi-dynamic testing method has been used because of the advantages that this method can offer for collectors with a unique construction, such as the proposed collector, over the steady-state testing method. With a quasi-dynamic testing method, it is possible to characterize the collector within a wide range of incidence angles and a complex incidence angle modifier profile. The proposed novel collector has a gross area of 2.57 m2. A maximum power output per collector unit area of 1140 W is found at 0 °C reduced temperature (1000 W/m2 irradiance level), while at a higher reduced temperature (70 °C), it drops down to 510 W for the same irradiance level. The data have been fitted through a multiple linear regression method, and the obtained efficiency curve coefficients are 0.39, 0.192, 1.294, 0.023, 0.2, 0, −5929 and 0 for Kθd, b0, c1, c2, c3, c4, c5 and c6, respectively. The experimental characterization carried out on the collector proved that the output powers calculated by using the obtained parameters of the quasi-dynamic testing method are in good agreement with experimental points.

The determination and prediction of the apparent reaction rates between excited triplet-state DOM and selected PPCPs

To determine and predict the reaction rate between 3DOM* and PPCPs in various water bodies, this study defines a reaction rate coefficient (α3DOM∗) to describe the reaction between 3DOM* and PPCPs. As the values also included the inhibition effect of DOM's antioxidant moieties, the calculation of α3DOM∗ is inconsistent with that of a bimolecular rate constant via the steady-state kinetic method. The α3DOM∗ values of 12 selected PPCPs were determined in two DOM solutions and ten DOM-containing water samples collected from typical surface water bodies in Beijing. The Pearson coefficients between nine predictors including the absorbance ratio (E2/E3), specific absorption coefficient at 254 nm (SUVA254), fluorescence index (FI), biological index (BIX), humification index (HIX), pH, total organic carbon (TOC), total fluorescence intensity (TFI) and TOC normalized TFI (TFI/TOC) and α3DOM∗ were examined. Correlation patterns for sulfonamides, β-blockers and diclofenac supported the electron transfer pathway, and was distinctly different from those appeared for FQs where quenching effect played a main part. TFI and TFI/TOC were recognized as the most useful surrogates in empirically predicting α3DOM∗. For PPCPs that went through the electron transfer pathway, α3DOM∗ could be well fit to the Rehm-Weller model assuming a proportional relationship between TFI and △Get. For FQs, α3DOM∗ was found to linearly correlated with TFI/TOC. The α3DOM∗ values determined in this study enrich the database of PPCPs photolysis parameters, and the correlation analysis provides reference for forecasting PPCPs fate in the aquatic environment.

An Efficient Construction Method of the 3D Random Asphalt Concrete Model Based on the Background Grid and the Moving-and-Densifying Algorithm

In order to avoid the tedious and time-consuming measuring process for thermal conductivity, many random models have been proposed, but the construction of those random models is still inefficient, which limits the further application. In this paper, a construction method of three-dimensional random asphalt models for predicting thermal conductivity based on the background grid and the moving-and-densifying algorithm was proposed which greatly improves construction efficiency. The influence of the random factors on models’ stability was studied and the range of the key factors within all random factors was restricted. Further, a conflict judgment method for the convex aggregate and the improved take-and-place method based on the background grid method and the moving-and-densifying algorithm was realized by MATLAB code to construct aggregate mixture models. Finally, the aggregate mixtures model was imported into ABAQUS 2022 to predict the thermal conductivity based on the steady-state plate method, and the validity of the predicting result was verified by experimental result. With this construction method, the stability index is improved by more than 80.71%, and packing efficiency is 198.98% higher than before. Additionally, the 3D random model showed a smaller prediction error range (less than 5%) than the 2D models (more than 10%) and was more accurate than the 2D prediction model. This research focused on improving the construction efficiency of the 3D random asphalt concrete model which contributes to full utilization and laying a foundation for further improvement.

INSTALLATION FOR DETERMINING THE THERMAL CONDUCTIVITY OF PLATES BY THE STATIONARY METHOD

When measuring the thermal conductivity of thermal insulation materials made by powder metallurgy and building porous materials, complications arise due to the fact that heat flows through the samples are commensurate with heat losses. The steady-state heat flow (SSHF) method is simple, does not require sophisticated equipment, and allows determining the thermal conductivity not in the near-surface layer but in the entire sample volume. Its disadvantage is low accuracy and the need to use reference samples. This work aims to develop an installation for measuring the thermal conductivity of largesized samples of low-conductivity material using the steady-state heat flow method with significantly higher accuracy than existing installations using this method. This is achieved by sandwiching the sample, which is a thin square plate of large dimensions, between the heater chamber and the refrigerator. The heating chamber is made of insulating material and its front wall, which is in contact with the sample, is made of the copper plate (which has good thermal conductivity). In the operating mode, the temperature in the heater chamber is maintained equal to the ambient temperature, which allows us to neglect heat losses and assume that in the steady-state mode, the heater power is equal to the heat flux through the sample. The thickness of the sample is much smaller than the size of its side (the sample should be square). This assumption is necessary to use the condition of isotropic temperature distribution in the cross-section of the sample. The refrigerator is filled with water and ice. The isotropic temperature distribution in the sample is ensured by its contact with the copper walls of the heater and refrigerator chamber. The temperature of the heated surface of the sample is measured using a thermocouple inserted through a hole in the front wall of the heater chamber. The proposed design of the installation and its operating conditions make it possible to significantly improve the accuracy of determining the thermal conductivity coefficient and make the error less than 2%.

Machine learning boosting the discovery of porous metamaterials with an abnormal thermal transport property

Normally, the introduction of porous structures into materials can tune their thermal conductivity, showing great applications in thermal management and thermoelectric energy harvesting. However, the ability of disorder changing the thermal conductivity of porous materials has seldom been explored. In this work, we show that an introduction of disorder into the macroscopic porous materials with a certain porosity can lead to a desired effective thermal conductivity over a large range, where an abnormal enhancement of ∼7.9% and a normal reduction of ∼44% at room temperature are predicted by the machine-learning-optimized algorithm. All of these theoretical calculation results are further verified by our experiments performed in the current work by using the steady-state thermal flux method. Moreover, when these periodic units are artificially connected, a structural anisotropy up to 40 is achieved, which can be further used to adjust the direction of the thermal flux in a well-controlled way. Our work provides an efficient and convenient approach for designing high-performance porous materials with specific thermal conductivity and high structural anisotropy for various applications in thermal management.

Effect of Heterogeneity on Capillary Pressure and Relative Permeability Curves in Carbonate Reservoirs. A Case Study for Mishrif Formation in West Qurna/1 Oilfield, Iraq

The special core analysis tests were accomplished on a set of core plugs for Mishrif Formation (mA, mB1, and mB2cde/mC units) in West Qurna/1 oilfield, southern Iraq. Oil relative permeability (Kro) data and the Corey-type fit of the data as functions of the brine saturation at the core outlet face for individual samples in the water-oil imbibition process to estimate relative permeability measurements by the centrifuge method were utilized. Identical correlations for oil and water relative permeabilities were extracted by steady-state and unsteady-state methods. For the mA samples, the gas-water capillary pressure curves were within a narrow range (almost identical) indicating that mA is a homogeneous unit. Kro curves for three mB2ab plugs were practically identical, that is referring to the homogeneity in the upper portion of the unit. The mB2 unit has a more solid‐phase concentration than other units. In addition, the general trend of low residual oil saturation is related to the raising in porosity but no reliable correlation between the residual oil saturation to water drive (Sorw) and Klinkenberg-corrected permeability (Kinf). Based on the correlation between the effective oil permeability at the initial water saturation [ko(Swi)] and (Kinf/f)1/2 for the high-permeability lithofacies mB1 plugs, ko(Swi) is approximately equal to or exceeds Kinf. While ko(Swi) was below Kinf for the other samples. New good empirical equations were obtained for effective gas permeability at final water saturation versus Kinf, as well as, for Kro and Krw versus saturation for all lithofacies.

Experimental and numerical prediction of LBO performance in a centrally staged combustor

A new type of centrally staged combustor was proposed for an aeroengine combustor with a fuel–air ratio of 0.037. The combustor dome comprised a three-stage swirler, which included a pilot stage and main stage. The pilot stage was composed of Stage 1 and Stage 2 swirlers, and all swirlers were radial. The effects of different inlet Reynolds numbers and swirler structural parameters, including the installation angle of the first radial swirler, installation angle of the second radial swirler, installation angle of the main stage, and co– and counter-rotation of Stage 1 and Stage 2 swirlers on the lean blow-out (LBO) performance of the centrally staged combustor were examined at an atmospheric pressure and inlet temperature of 473 K. Experiments with single-dome rectangular test pieces and numerical methods were used. The results showed that the fuel–air ratio decreases with an increase in the inlet Reynolds number, indicating that the increase in inlet Reynolds number plays an important role with respect to the LBO. When the rotation directions of Stage 1 and Stage 2 swirlers were opposite, the fuel–air ratio of the LBO was smaller than that of Stage 1 and Stage 2 swirlers in the same rotation direction, indicating that the rotation directions of Stage 1 and Stage 2 swirlers significantly affect the LBO performance. Stage 1 and Stage 2 swirlers exhibited the best LBO performance when they rotated in opposite directions, and the rotation direction of the main stage slightly affected the LBO performance. The best combination of rotation directions is that the rotation directions of Stage 1 and Stage 2 swirlers should be opposite and rotation direction of Stage 2 swirler should be the same as that of the main stage. With the increase in the installation angle of Stage 1 and Stage 2 swirlers, the LBO fuel–air ratio decreased by nearly 4% and 9%, respectively, and the LBO performance improved. The prediction of the LBO limit of 0.00553, using the fuel steady-state successive approximation method, was less than 0.0066, which was measured in the test, indicating that the method should be improved. The flow field characteristics of the LBO process, which could not be obtained in the test process, were obtained via numerical simulation.

Differential Behavior of Eicosapentaenoic and Docosahexaenoic Acids on the Organization, Dynamics, and Fusion of Homogeneous and Heterogeneous Membranes.

Membrane fusion is a common course in innumerable biological processes that helps in the survival of eukaryotes. Enveloped viruses utilize this process to enter the host cells. Generally, the membrane lipid compositions play an important role in membrane fusion by modulating the membrane's physical properties and the behavior of membrane proteins in the cellular milieu. In this work, we have demonstrated the role of polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, on the organization, dynamics, and fusion of homogeneous and heterogeneous membranes. We have exploited arrays of steady-state and time-resolved fluorescence spectroscopic methods and polyethylene glycol-induced membrane fusion assay to elucidate the behavior of EPA and DHA on dioleoyl phosphatidylcholine (DOPC)/cholesterol (CH) homogeneous and DOPC/sphingomyelin/CH heterogeneous membranes. Our results suggest that EPA and DHA display differential effects on two different membranes. The effects of PUFAs in homogeneous membranes are majorly attributed to their flexible chain dynamics, whereas the ability of PUFA-induced cholesterol transfer from the lo to the ld phase rules their behavior in heterogeneous membranes. Overall, our results provide detailed information on the effect of PUFAs on homogeneous and heterogeneous membranes.

P-bifurcation phenomena of the non-smooth modified rayleigh-duffing oscillator under the combined action of harmonic excitation and noise perturbation

In this paper, the stochastic dynamics of a modified Rayleigh-Duffing oscillator with Coulomb frictional damping and elastic impact is investigated under combined harmonic and noise excitations. On the premise of retaining the non-smooth properties, a non-smooth steady-state probability density response numerical calculation method is introduced by taking advantage of Markov process. Utilizing this method, the stochastic P-bifurcation phenomena of oscillators without and with externally excitation are discussed in detail by inscribing changes in the topology of the steady-state probability density function. It is displayed that certain nonlinear damping coefficient and external excitation amplitude change the structure of the response, and that both the friction coefficient and the elastic coefficient of the contact surface induce stochastic P-bifurcation phenomena in systems without and with harmonic excitation, respectively. This study reveals the effect of non-smooth factors on the stability of the Rayleigh-Duffing oscillator.

Mass Transfer through Vapor–Liquid Interfaces Studied by Non-Stationary Molecular Dynamics Simulations

Molecular dynamics (MD) simulations are highly attractive for studying the influence of interfacial effects, such as the enrichment of components, on the mass transfer through the interface. In a recent work, we have presented a steady-state MD simulation method for investigating this phenomenon and tested it using model mixtures with and without interfacial enrichment. The present study extends this work by introducing a non-stationary MD simulation method. A rectangular simulation box that contains a mixture of two components 1 + 2 with a vapor phase in the middle and two liquid phases on both sides is used. Starting from a vapor-liquid equilibrium state, a non-stationary molar flux of component 2 is induced by inserting particles of component 2 into the center of the vapor phase in a pulse-like manner. During the isothermal relaxation process, particles of component 2 pass through the vapor phase, cross the vapor-liquid interface, and enter the liquid phase. The system thereby relaxes into a new vapor-liquid equilibrium state. During the relaxation process, spatially resolved responses for the component densities, fluxes, and pressure are sampled. To reduce the noise and provide measures for the uncertainty of the observables, a set of replicas of simulations is carried out. The new simulation method was applied to study mass transfer in two binary Lennard-Jones mixtures: one that exhibits a strong enrichment of the low-boiling component 2 at the vapor-liquid interface and one that shows no enrichment. Even though both mixtures have similar transport coefficients in the bulk phases, the results for mass transfer differ significantly, indicating that the interfacial enrichment influences the mass transfer.

Unsteady Heat Flux Measurement and Predictions Using Long Short-Term Memory Networks

Energy consumption modeling has evolved along with building technology. Modeling techniques can be largely classified into white box, gray box, and black box. In this study, the thermal behavior characteristics of building components were identified through time-series data analysis using LSTM neural networks. Sensors were installed inside and outside the test room to measure physical quantities. As a result of calculating the overall heat transfer coefficient according to the international standard ISO 9869-1, the U value of the multi-window with antireflection coating was 1.84 W/(m2∙K). To understand the thermal behavior of multiple windows, we constructed a neural network using an LSTM architecture and used the measured data-set to predict and evaluate the heat flux through deep learning. From the measurement data, a wavelet transform was used to extract features and to find appropriate control time-step intervals. Performance was evaluated according to multistep measurement intervals using the error metric method. The multistep time interval for control monitoring is preferably no more than 240 s. In addition, multivariate analysis with several input variables was performed. In particular, the thermal behavior of building components can be analyzed through heat flux and temperature measurements in the transient state of physical properties of pre-installed building components, which were difficult to access with conventional steady-state measurement methods.

Probe beam influence on spin polarization in spin-exchange relaxation-free co-magnetometers

Spin-exchange relaxation-free (SERF) co-magnetometers have promising applications in both inertial navigation and fundamental physics experiments. However, the fluctuation in the spin polarization caused by the probe beam has a non-negligible influence on the co-magnetometer signal. In this paper, a theoretical model containing three parameters of the probe beam is established by extending the coupled Bloch equation. Based on this model, the influence of probe power density on the transient and steady-state response of the SERF co-magnetometer is analyzed. According to the transient response model, a new measurement method for transverse optical pumping of the probe beam is proposed. Then, for the steady-state response model, a steady-state error suppression method is suggested by adjusting the degree of circular polarization of the probe beam. Eventually, the suppression method is used to refine the SERF co-magnetometer, achieving a suppression rate of 70.31% in transverse electron spin polarization fluctuations, thus improving the co-magnetometer to a stability of 0.0079∘ h−1. To our knowledge, this is better than what has been reported so far.

Thermal conductivity assessment of moist building insulation material using a Heat Flow Meter apparatus

Thermal conductivity is one of the most important parameters of building insulation materials. This parameter is dependent on the temperature, and on the moisture content for hygroscopic materials. When measured by steady-state methods (with the HFM device and the guarded hot plates), moisture will migrate from the hot side to the cold, influencing the measured heat flux and, thus, the measured thermal conductivity. This study aims to analyze the effects of moisture transfer on the thermal conductivity measurement of wet hygroscopic light building insulation material (namely wood fiber insulation). Several experiments are performed on instrumented samples to evaluate the influence of parameters like the thickness, the mean moisture content, the mean temperature, or the temperature gradient on the measured heat flux, on the temperature and relative humidity distributions and on the time to reach hygrothermal equilibrium. Particularly, the measurement errors made when shortening the experiment are discussed and the moisture dependence of true thermal conductivity is evaluated experimentally by considering the notions of apparent and diffusive thermal conductivities. Last, by using a validated heat and moisture transfer model, this dependency is compared to the one predicted by the methods proposed in the standards EN 12664 or ISO 10051.

Recognition of Oil Content for Oil Shale by Electronic Nose Based on Transient and Steady-State Fusion Feature Extraction Method

The evaluation of oil shale is significant to oil and gas exploration. Electronic nose (E-nose) has excellent odor recognition characteristics and can be used as a potential tool for oil content recognition. In this article, the odor samples of Huadian and Wangqing oil shale with different oil contents were obtained, and the recognition ability and feasibility of E-nose on oil content were investigated for the first time. More comprehensive information of oil shale was obtained by using transient and steady-state fusion feature (TAS) extraction method, which improves the recognition rate, and the influence of feature extraction methods and temperatures on oil content recognition were further discussed. The experimental results show that the E-nose combined with the proposed feature extraction method can realize the rapid in situ recognition of oil content at low temperatures. This work will help to propose more effective methods for the evaluation and development of oil shale.

Pie-rolling-inspired construction of vertical carbon fiber high thermal conductivity hybrid networks

Carbon fiber (CF) with a high thermal conductivity (Tc) of 1100 W m−1 K−1 along its one-dimensional (1D) direction is considered a promising filler for fabricating high-performance thermal interface material (TIM). However, Tc in the radial direction of CF is far less than 10 W m−1 K−1 determines that Tc highly depends on the orientation of CF. In this study, polydimethylsiloxane (PDMS)/short carbon fibers (SCFs)/Al spherical particle (PDMS/SCFs/Al) composite is firstly prepared. SCFs are then arranged into horizontal (0°), inclined (45°), and vertical (90°) orientations, respectively, utilizing a convenient “pie-rolling” method that does not rely on any specific instrument. As a result, the vertically oriented SCFs together with Al spherical particles establish an effective thermal conductivity-three-dimensonal (3D) network, and the Tc of the through-plane is as high as 10.46 W m−1 K−1, while the in-plane Tc is 6.23 W m−1 K−1 measured from a steady-state method. The anisotropic thermal conductivity is also verified by a hot-disk method. The working mechanism and thermal conductivity of oriented SCFs and Al spherical particles composites are being studied using finite element simulation. In addition, the change in surface temperature of the composites during heating and cooling stage is observed using an infrared thermal imaging camera. A 16 ℃’s temperature decline demonstrates that the high-efficiency heat transfer along the vertical orientated carbon fiber-based 3D network was successfully realized in SCF-90 when it was used as a TIM between a bare die and heat pipe of a laptop. This work illustrates the prospect of using SCFs to prepare a high thermally conductive 3D network could be used in the future thermal management of electronic devices.

Detection of the Dark States in Thermally Activated Delayed Fluorescence (TADF) Process of Electron Donor-Acceptor Dyads: Insights from Optical Transient Absorption Spectroscopy.

The photophysical processes involved in the electron donor-acceptor thermally activated delayed fluorescence (TADF) emitters are complicated and controversial. The recent consensus is that at least three states are involved, i. e. the singlet charge transfer state (1 CT), the triplet localized excited state (3 LE) and the triplet CT state (3 CT). It is clear the very often used steady state and time-resolved luminescence spectroscopic methods are unable to present direct evidence for the dark states, i. e. the 3 LE and 3 CT states, as well as the interconversion of these states. Concerning this aspect, the femtosecond-nanosecond transient absorption spectroscopic methods are in particular interests. Both the emissive state and the dark state can be detected in these spectra, and interconversion of the states involved in TADF process can be also revealed. This review article focuses on the recent development of using the transient absorption spectra to study the photophysics of the TADF emitters.

Experimental investigation of formation damage during drilling of ultradeep fractured carbonate reservoir

Severe formation damage easily occurs in ultradeep fractured carbonate reservoirs during drilling, yet the formation damage mechanisms have not been studied extensively. This study focused on typical fractured carbonate reservoirs in the Shunbei field, China. The multiscale reservoir space characteristics and core wettability of ultradeep fractured carbonate reservoirs were investigated. The results showed that the reservoirs mainly comprise a fourth-order fracture network. The high-temperature and high-pore-pressure steady-state method also identified fluid sensitivity and phase trapping damage. The fluid sensitivity damage at the formation temperature (170 °C) indicated that this reservoir is affected by water sensitivity, salt sensitivity (critical value: 3/4 formation water salinity (FWS)), alkali sensitivity (critical value: pH 7.5), and liquid phase trapping damage. Particle movement and deposition and liquid phase trapping damage are thought to be the primary damage mechanisms. Furthermore, abnormally low water saturation, mixed wettability, abundant clay minerals, and the fourth-order fracture network contribute to fluid sensitivity and liquid phase trapping damage. Finally, a formation damage control strategy was proposed.