Concave Surface Research Articles

Preparation of Golf Ball-like Polymer Particles Bearing Site-Selective Functional Groups.

Golf ball-like particles have emerged as interesting materials in the fields of therapeutics, diagnostics, chemical sensing, etc. because of their unique shapes (with concave and convex moieties) and physical properties. Despite their uniqueness, their surfaces are generally covered with single components lacking functional groups, and a well-established functionalization method for a specific area of these particles, such as their concave or convex surface, is lacking. Thus, we proposed a seeded-dispersion polymerization (SDP)-based method for preparing anionic- and cationic-group-bearing golf ball-like polymer particles mainly on their convex surface. Briefly, we prepared golf ball-like particles with site-selective functional groups by subjecting n-butyl methacrylate (nBMA) to SDP in the presence of polystyrene-seed particles and dodecane using 2,2'-azobis(isobutyronitrile) as an initiator; this yielded a poly(nBMA), PnBMA, concave phase. The shape of the golf ball-like particles was also controlled by adjusting the nBMA amount and solvent composition. Further, the results revealed that the functional groups were introduced onto the convex surface of the golf ball-like particles, and the position of the ionic groups on the particles was confirmed based on metal-nanoparticle adsorption. Thus, we demonstrated the feasibility of preparing convex surfaces of golf ball-like particles to impart such surfaces with anionic or cationic functional groups, thereby expanding the application scope of these heteromorphic particles.

Thermo-hydro-mechanical modelling of the heterogeneous subsidence and swelling in the desiccation cracked clayey strata

Soil desiccation cracking as a consequence of severe environmental changes alters soil deformation mechanisms significantly. Therefore, this study aims to explore the effect of crack characteristics and environmental conditions on the heterogeneous deformation of desiccation-cracked soils using thermo-hydro-mechanical analyses. The model framework consists of balance equations, thermal, hydraulic, and mechanical constitutive equations, while the model scenarios were determined based on statistical analyses. The meteorological record of Qom city was used for three years, from 2015 to 2017, to capture long-term behaviour under wetting-drying cycles. Findings revealed that cracks extend the deformation range, potentially up to six times, with variation based on crack dimensions and spacing. Notably, narrower cracks experienced more pronounced deformation than wider ones. The cracked soil with a crack depth of 2.5 m showed 1.5 times higher swelling and subsidence than crack depth of 1 m. Furthermore, the wider cracks indicated a lower rate of increase in their dimensions compared to the initial state during drying. The investigation also highlights the mechanisms of soil surface shape due to swelling and shrinkage, resulting in concave and convex surfaces, respectively. The results provide new perspectives on the behaviour of fine-grained deposits in arid to semi-arid climates with deep groundwater levels.

Developing Deformable Facets for Heliostats: An Increased Solar Concentration for Thermochemical Applications with Central Tower Receivers

In the present article a new design of a deformable facet and a heliostat with several deformable facets is presented. Previous work has been made around designing heliostats with concentrating facets in the facilities of the Plataforma Solar de Hermosillo. The evaluation and design process of facets and their evolution is also shown and reviewed. The facet design was initially conceived as a parabolic trough surface, however, through a modification of the facet, the surface was transformed into a concave surface. The resulting spot produced by the facet assumes nearly a spherical surface. A heliostat constructed with these facets shows similar optical performance with a previous one made with spherical facets; this spherical heliostat has a higher peak and mean flux. Nevertheless, the deformable facet heliostat presents a simpler construction and structure. A comparison between both heliostats will be presented.

Methane Adsorption and Transport in Tortuous Slit-like Nanochannels: A Molecular Simulation Study.

Tortuosity is a crucial characteristic of porous materials, such as the shale matrix where shale gas is stored. The presence of tortuous nanochannels significantly affects the adsorption and transport of nanoflows. In this research, we use molecular dynamics simulation (MD) to study the adsorption and transport properties of shale gas (methane) in a curved slit-like nanochannel constructed from bent graphene sheets. Our findings reveal that the curvature of the tortuous channel influences methane adsorption: convex surfaces exhibit stronger adsorption, while concave surfaces exhibit weaker adsorption; the discrepancy is amplified by the nanoflow. Additionally, nanoflow velocity is heterogeneously distributed within the curved channel, with higher tangential flow velocities observed near the entrance and the outer surface. We also identify a "bouncing effect", where the nanoflow not only moves tangentially along the channel but also bounces between the inner and outer walls. Furthermore, methane in narrower channels exhibits higher tangent flow velocity and higher bouncing frequency but smaller flux, whereas larger curvature results in shorter channel length and smaller tortuosity, but the transport tangent velocity and flux are both reduced. The findings of this study can help in the better understanding of shale gas nanoflow properties in tortuous media and provide insights for simulating more general nonstraight nanoflows.

Fabrication, characterization and simulated gastrointestinal digestion of sea buckthorn pulp oil microcapsule: effect of wall material and interfacial bilayer stabilization.

Sea buckthorn (Hippophae rhamnoides L.) pulp oil is rich in functional components; however, low water solubility and stability limit its applications. This study fabricated sea buckthorn pulp oil microcapsules using whey protein isolate (WPI), soy protein isolate (SPI), sodium caseinate (NaCN), gum arabic (GA), starch sodium octenylsuccinate (OSAS) and SPI mixed with chitosan (CHI). The influences of these wall materials on physicochemical properties, release behavior and digestibility were explored. Protein-based wall materials (WPI, NaCN, SPI) demonstrated lower bulk densities due to their porous structures and larger particle sizes, while GA and OSAS produced denser microcapsules. Encapsulation efficiency was the highest for protein-based microcapsules (79.41-89.12%) and the lowest for GA and OSAS. The surface oil percentage of protein-based microcapsules (1.41-4.40%) was lower than that of the other microcapsules. Protein-based microcapsules showed concave and cracked surfaces, while GA and OSAS microcapsules were spherical and smooth. CHI improved reconstitution performance, leading to faster dissolution. During simulated gastrointestinal digestion, protein-based microcapsules released more free fatty acids (FFAs) in the intestinal phase, while CHI-modified SPI microcapsules showed a delayed release pattern due to thicker walls. Protein-based wall materials were more effective for sea buckthorn pulp oil microencapsulation, providing higher encapsulation efficiency, better flow properties and releasing more FFAs. The addition of CHI led to the layer-by-layer self-assembly of the microcapsule wall and resulted in sustained release during in vitro intestinal digestion. These findings suggested the potential of protein-based microcapsules for targeted delivery and improved applications of bioactive oils in the food industry. © 2024 Society of Chemical Industry. Published by John Wiley & Sons Ltd.

A compact stem-loop DNA aptamer targets a uracil-binding pocket in the SARS-CoV-2 nucleocapsid RNA-binding domain.

SARS-CoV-2 nucleocapsid (N) protein is a structural component of the virus with essential roles in the replication and packaging of the viral RNA genome. The N protein is also an important target of COVID-19 antigen tests and a promising vaccine candidate along with the spike protein. Here, we report a compact stem-loop DNA aptamer that binds tightly to the N-terminal RNA-binding domain of SARS-CoV-2 N protein. Crystallographic analysis shows that a hexanucleotide DNA motif (5'-TCGGAT-3') of the aptamer fits into a positively charged concave surface of N-NTD and engages essential RNA-binding residues including Tyr109, which mediates a sequence-specific interaction in a uracil-binding pocket. Avid binding of the DNA aptamer allows isolation and sensitive detection of full-length N protein from crude cell lysates, demonstrating its selectivity and utility in biochemical applications. We further designed a chemically modified DNA aptamer and used it as a probe to examine the interaction of N-NTD with various RNA motifs, which revealed a strong preference for uridine-rich sequences. Our studies provide a high-affinity chemical probe for the SARS-CoV-2 N protein RNA-binding domain, which may be useful for diagnostic applications and investigating novel antiviral agents.

Evolution of supersonic cooling film flow over concave and convex surfaces with different radius curvatures

A cooling film (Mach 2.3) is injected into a supersonic wind tunnel's (Mach 3.8) flow field. As the curvature radius decreases, mixing layer destabilization is delayed on the CV (convex wall) and advanced on the CC (concave wall). When x = 20–60 mm, wall pressure is influenced by the cooling film, and when x = 100–220 mm, curvature dominates. As the curvature radius decreases, pressure on the concave wall increases more rapidly, while that on the convex wall decreases more swiftly. IP (impulse for bulk dilation) values on the CC-1500 and CV-1500 walls are approximately twice those on the CC-3000 and CV-3000 walls, respectively.

Interfacial characterization of spinning water film along a concave wall

Abstract Thin liquid film flowing down the inner concave surface of a vertical cylindrical vessel is examined. At the top of the vessel, the water is injected horizontally at high speed circumferentially along the vessel wall and flows downwards due to the action of gravity. This turbulent film flow is modeled using the large eddy simulation (LES) and Reynolds averaged Navier–Stokes (RANS) approaches combined with the volume-of-fluid method. The results of both methods are validated with direct numerical simulation. The Favre-filtered two-phase LES, which is implemented and studied in this paper, can reasonably predict the film thickness similarly to that of the RANS approach using the elliptic blending Reynolds stress model, although it requires fine resolution in the wall region. The effect of volume flow rate on the film structure and thickness is investigated. The film thickness is shown to be nearly constant when the wall is partially wetted and changes as the cubic root of the volume flow rate when the spinning film encloses the entire circumference of the vessel.

Enhancing Savonius Rotor Performance with Zigzag in Concave Surface-CFD Investigation

Savonius, a type of vertical-axis wind turbine (VAWT), is suitable as an appropriate small-scale energy conversion apparatus for regions with relatively low wind speeds, such as Indonesia; however, it exhibits sub-optimal efficiency. One potential approach to improving the efficiency of Savonius turbines is to increase the drag force on the concave surface of the blades. In this case, the dissimilarity in the forces experienced by the two blades can be increased, resulting in a corresponding increase in torque. This investigation aims to assess and compare the power coefficient (Cp), torque and drag coefficient (Cd) of the conventional Savonius rotor with the zigzag pattern implemented in the middle area of the concave surface of the blades at low wind speeds. The efficiency can be achieved by implementing the k-ω shear stress transfer (SST) turbulent model and 3D computational fluid dynamics simulation at tip speed ratio (λ) 0.4-1 with a velocity inlet of 4, 5, and 6 m/s. The study results show that using the zigzag pattern on the concave surface led to an 18.8% boosted in Cp of at λ = 0.8 and an inlet velocity (U) = 5 m/s compared to the standard Savonius rotor model. In this case, the efficiency of the Savonius wind turbine may be enhanced by incorporating a zigzag pattern in the middle of the concave surface of the Savonius rotor.

MODELING GROWTH AND VISCOUS FLOW OF OXIDE ON CYLINDRICAL SILICON SURFACES INCLUDING PIEZOVISCOUS INHIBITION

Abstract A baseline constant-parameters non-dimensional cylindrical oxidation model was first revisited, normalizing oxide thickness to oxidant diffusivity/reaction rate ratio instead of original cylinder radius, allowing this radius to remain evident in model output, which in this baseline case predicted oxides increasingly thicker for convex surfaces of decreasing radius as compared to that on flat surface, with oxide thicknesses on concave surfaces instead predicted to decrease with decreasing radius from the flat case. As this convex behavior conflicts with reported experiment, where oxide thickness on convex surfaces rather decrease with decreasing radius from the flat case though less strongly than for concave surfaces, potential stress-dependent kinetics parameters were investigated, with stresses determined from viscous treatment of oxide flow during growth to accommodate its molecular volume exceeding that of the silicon consumed in its production. While oxidant diffusivity and solubility both considered to increase with increasing hydrostatic pressure instead cause model predictions to further deviate from experimental observation, the rate of its volume-producing reaction with the silicon considered to decrease with increasingly compressive radial stress across their interface successfully brought model predictions of convex curvatures into agreement with reported experiments. In conjunction with such stress-dependent reaction rate, additional consideration of viscosity as increasing with hydrostatic pressure can also contribute towards bringing convex modeling closer to experimental observation, though it also introduces a potential piezoviscous inhibition where concave cases of smaller curvature radius become predicted incapable of even initiating oxidation.

The sandwich feeding assay for use with first instar nymphs of the Asian citrus psyllid, Diaphorina citri confirms the high susceptibility of this life stage to bacterial pesticidal proteins

Citrus greening or huanglongbing is the most important disease of citrus and threatens citrus production worldwide. As nymphs of Diaphorina citri play a crucial role in the acquisition and transmission of the citrus greening bacterium, suppression of this life stage is particularly important. However, the lack of a tractable feeding assay for use with first instar D. citri nymphs has impeded assessment of the toxicity of bioactives. Of several bacterial pesticidal proteins (BPP) that are toxic to D. citri adults, Mpp51Aa1 and Cry1Ba1, which have LC50 values of 110 and 120 µg/mL respectively in adults, were fed to 1st instar nymphs in a newly developed assay. For this new sandwich feeding assay, parafilm layers containing feeding solution were placed on top of two 35 mm Petri dishes, with a concave surface created on each. Fifty nymphs were transferred to the membrane on one Petri dish, and the second Petri dish placed on the top to create a “sandwich” with the 1st instar nymphs in the middle. Nymphs were fed for four days and the LC50 values for Mpp51Aa1 and Cry1Ba1 were calculated at 6.7 and 41.6 µg/mL respectively. Bioassays with bioengineered plants expressing Cry1Ba1 confirmed that the majority of D. citri mortality occurs during the 1st instar nymph stage, while egg laying adults are much less susceptible. Taken together, these results confirm that 1st instar D. citri nymphs are more susceptible to BPP than adults and demonstrate the utility of the sandwich feeding assay for effective screening of BPPs prior to investment into production of transgenic plants.

The Generation Mechanism of the Side Force and Yawing Moment of a Rotating Missile with Wrap-Around Fins

The rotation of a missile generates a side force perpendicular to the plane containing the attack angle and produces a yawing moment that tilts the body out of the plane, significantly affecting the flight stability of rotating missiles. The non-planar asymmetry of the wrap-around-fin rotating missile determines its more complex rotational effects. This study utilizes the dual time-step method to solve the unsteady Navier–Stokes equations, investigating the characteristics of the side force and yawing moment of the wrap-around-fin rotating missile under supersonic conditions and uncovering the mechanism behind the generation of the side force and yawing moment. The results reveal that the side force and yawing moment of the wrap-around-fin missile are composed of static values and induced values from rotation. The static side force and yawing moment of the wrap-around-fin missile are not zero, while those of the flat-plate-fin missile are zero. This difference is primarily caused by the non-axisymmetric nature of the wrap-around fin, resulting in the static side force and yawing moment of the wrap-around-fin missile being 40% greater than those of the flat-plate-fin missile. The rotation of the missile increases the effective angle of attack on the convex surface of the fin and decreases it on the concave surface, leading to an imbalance in the pressure changes on the windward and leeward sides. This is the main reason for the generation of the induced side force and yawing moment due to rotation. The induced values from rotation vary linearly with the rotation rate, and their magnitudes can be several times those of the static values.

Continuous Homogeneous Thin Liquid Film on a Single Cross-Shaped Profiled Fiber with High Off-Circularity: Toward Quick-Drying Fabrics.

Quick-drying fabrics, renowned for their rapid sweat evaporation, have witnessed various applications in strenuous exercise. Profiled fiber textiles exhibit enhanced quick-drying performance, which is attributed to the excellent wicking effect within fibrous bundles, facilitating the rapid transport of sweat. However, the evaporation process is not solely influenced by macroscopic liquid transport but also by microscopic liquid spreading on the fibers where periodic liquid knots induced by spontaneous fluidic instability significantly reduce the evaporation area. Here, a cross-shaped profiled fiber with high off-circularity, featured as multiple concavities along the fibrous longitude-axis, which enables the formation of a homogeneous thin liquid film on a single fiber without any periodic liquid knots, is developed. The high off-circularity cross-sections help overcoming Plateau-Rayleigh instability by tuning the Laplace pressure difference, further facilitated by capillary flow along the concave surface. The homogeneous thin liquid film on a single fiber is responsible for maximizing the evaporation area, resulting in excellent overall evaporation capacity. Consequently, fabrics made from such fibers exhibit rapid evaporation behavior, with evaporation rates ≈50% higher than those of cylindrical fabrics. It is envisioned that profiled fibers may provide inspiration for the manipulating homogeneous liquid films for applications in fluid coatings and functional textiles.

Occurrence of methane in organic pores with surrounding free water: A molecular simulation study

Free water contained in shale reservoirs can influence the enrichment and transportation of shale gas. To accurately assess shale gas adsorption in shale reservoirs and improve recovery, it is crucial to understand the occurrence of gas and water. In this study, the occurrence of methane occupying the organic pores surrounded by free water is investigated using Grand Canonical Monte Carlo/Molecular Dynamics simulations, considering the effects of pressure, temperature and pore size. The center of the model represents methane adsorbed/free within the organic pores, while the regions on either side depict free water. Although water does not significantly penetrate organic pores, pressure, temperature, and pore size have a notable impact on the wettability of water on organic surfaces, resulting in variations in the concave liquid surface morphology. This results in varying degrees of competitive adsorption of water and methane near the carbonyl group. At lower pressures, although the capillary pressure decreases sharply with increasing pore size, the improved water wettability increases the extent of its intrusion along the pore surface, thereby enhancing the competitive adsorption of methane and water. At higher pressures, capillary pressure acts as a resistance, preventing water from invading the organic pores in significant quantities. Due to the weak affinity of organic pores for water, the same phenomenon was observed even after increasing the pore size and temperature to improve water wettability. In addition, high temperatures can lead to more pronounced water intrusion. Finally, it is hypothesized that competitive adsorption of methane and water is more pronounced at shallower burial depths and slightly larger pore sizes. This result is expected to provide insights for the accurate evaluation of gas adsorption in water-bearing shales.

A versatile 5-axis melt electrowriting platform for unprecedented design freedom of 3D fibrous scaffolds

Melt electrowriting (MEW) is an electrohydrodynamic additive manufacturing technology for the fabrication of precise microfiber scaffold architectures but is so far restricted to printing onto simple collector geometries and, therefore, constrained in design freedom. This is due to current limitations in print head designs, kinematic systems, and software to generate motion commands. We address these aspects by upgrading a low-cost 5-axis kinematic system and complete it with a custom-designed print head and a collector fabrication workflow to enable collision-free MEW onto arbitrarily shaped multicurvature 3D geometries. A universal graphical approach enables generation of Gcodes customized to the 5-axis MEW requirements. The print head is validated by producing polycaprolactone fibers with diameters ranging from 5.6 ± 1.7 µm to 50.7 ± 5.5 µm and by writing both linear and non-linear fiber patterns onto collectors featuring concave and convex surfaces. Stable printing conditions are achieved by continuously reorienting the print head and collector surface perpendicular to each other at a constant working distance. Ultimately, we demonstrate the system’s potential in shaping anatomically relevant scaffold geometries by stacking microfibers onto collectors resembling a trileaflet valve and a bifurcating vessel. This multi-axis MEW platform unlocks exciting avenues towards unprecedented design freedom for MEW scaffolds.

Hypersonic Stability and Breakdown Measurements on the AFRL/AFOSR BOLT II Flight Geometry

The Air Force Research Laboratory/Air Force Office of Scientific Research (AFRL/AFOSR) introduced the Boundary Layer Turbulence (BOLT II) flight experiment to further the understanding and modeling of a hypersonic turbulent boundary layer on a geometry that features concave surfaces with swept leading edges. In support of the flight experiment, this paper identifies and documents the transition instabilities and quantifies the breakdown to turbulence on a 25%-scale BOLT II model in hypersonic flow. Experiments were conducted in the conventional Actively Controlled Expansion wind tunnel facility and the Mach 6 Quiet Tunnel located at the Texas A&M University National Aerothermochemistry and Hypersonics Laboratory. Global surface heating was viewed using infrared thermography with on-surface measurements made using high-frequency Kulite and PCB Piezotronics surface pressure transducers. Modal growth was observed among the sensors both upstream and downstream of the model. Off-surface measurements were made in the mixed-mode region utilizing constant-temperature hot-film anemometry in the Mach 6 Quiet Tunnel. Comparisons were made to the Direct Numerical Simulation (DNS) results from the University of Minnesota. Amplified content was observed between f=53 and 75 kHz in the root-mean-square voltage fluctuations of the hot-film measurements.

Numerical investigation of the number of excitation elements-dependent acoustic field characteristics of a histotripter

Abstract Histotripsy is an emerging ultrasound technology for disintegrating various soft tissues noninvasively and accureately. However, it is difficult to characterize the acoustic field of a histotripter using the existing measurement methods (i.e., hydrophones) because of the damage potential of bubble cavitation on the sensing element under such high irradiation power. In this work, according to a quantitative relationship between the acoustic pressure and ultrasonic focusing gain G, nonlinearity β, attenuation coefficient α, a numerical reconstruction method is proposed to accurately and reliably estimate the acoustic field of a histotripter. The k-Wave toolbox was used to calculate the acoustic field produced from identical sectors on a common concave surface by gradually increasing the number of excitation elements (i.e., up to 256 that cover the whole surface). The excitation frequency is 0.8 MHz, and the initial pressure at the transducer surface is 0.4 MPa. The focusing gains, peak positive and negative pressure, positive to negative peak acoustic pressure ratio, and harmonic distributions in the focal region under different numbers of excited elements were analysed. It is found that when about a quarter of the transducer surface is excited (64 elements), the nonlinear effect becomes obvious, resulting in significant peak pressures and harmonics. Furthermore, the relationship between the positive and negative pressure peaks (p + and p ¬) and the number of excited elements fits a quadratic curve function quite well (R = 0.999). Altogether, the proposed method can be applied to estimate the acoustic pressure at an extremely high intensity that exceeds the range of current measurement apparatus. Acoustic pressures using a low number of excited elements are measured first and then extrapolated to the full surface coverage using the built-in regression models. In the near future, the field calculation scheme for the therapeutic focused transducers with higher irradiation power and larger dimensions, as well as experimental work, will be done to further validate our model.

Development of the BOLT-2 Roughness Experiment for Flight

A sounding rocket research flight called BOLT-2, which stands for Boundary Layer Turbulence 2, was initiated with the goal of studying hypersonic boundary-layer transition and turbulence. The BOLT-2 research vehicle is based on a three-dimensional geometry with concave surfaces and swept leading edges that provides two separate and distinct, also redundant, flowpaths for conducting measurements. One side of BOLT-2 is dedicated to smooth surface transition and turbulence, to better study the natural instability processes, whereas the other has been assigned to study forced transition and turbulence using discrete roughness trips. The present paper is intended to document the primary drivers and decisions made that lead up to finalizing the roughness-side experiment for the BOLT-2 flight.

Hydrogen Embrittlement Detection Technology Using Nondestructive Testing for Realizing a Hydrogen Society.

Crack detection in high-pressure hydrogen gas components, such as pipes, is crucial for ensuring the safety and reliability of hydrogen infrastructure. This study conducts the nondestructive testing of crack propagation in steel piping under cyclic compressive loads in the presence of hydrogen in the material. The specimens were hydrogen-precharged through immersion in a 20 mass% ammonium thiocyanate solution at 40 °C for 72 h. The crack growth rate in hydrogen-precharged specimens was approximately 10 times faster than that in uncharged specimens, with cracks propagating from the inner to outer surfaces of the pipe. The fracture surface morphology differed significantly, with flat surfaces in hydrogen-precharged materials and convex or concave surfaces in uncharged materials. Eddy current and hammering tests revealed differences in the presence of large cracks between the two materials. By contrast, hammering tests revealed differences in the presence of a half size crack between the two materials. These findings highlight the effect of hydrogen precharging on crack propagation in steel piping and underscore the importance of early detection methods.

Can rock surface flow derived from outcrops generate surface runoff in a rocky desertified area?

Rock surface flow, formed from exposed rock surfaces, is a unique form of runoff in rocky desertified areas with massive bedrock outcrops. The question of whether the rock surface flow promotes surface runoff formation continues to puzzle us. To address this problem, four sites with notable bedrock outcrops and different land use types were selected from a typical desertified area in Guizhou, China. Straight and concave rock-surface shapes that were the most capable of collecting rainwater were selected at each site. Soil infiltration and water storage capacity experiments were conducted to observe the infiltration and water storage properties of the soil closely adhering to the rock–soil interface (CRSI) of the bedrock outcrops by taking the soils far from the outcrops horizontally (FRSI) as the control, and to further explain the conditions for surface runoff formation via rock surface flow. Our results showed that the CRSI is more prone to producing surface runoff than the FRSI, which is attributed to its lower infiltration (stable infiltration rate of 0.2 to 192.6 mm/min) and water storage capacity (total reservoir 441.6 to 613.6 t/hm2) than that of FRSI (4.50 to 272.8 mm/min, 458.8 to 635.4 t/hm2). This phenomenon would be intensified after receiving the rock surface flow input. Concurrently, concave rock surfaces are more likely to promote surface runoff formation than straight rock surfaces, which are affected by the accumulation of rock surface shapes on rainwater. A discriminating condition for whether rock surface flow produces surface runoff at the CRSI is proposed based on the inversely proportional functional relationship between rainfall (rainfall intensity RI and amount RA) and the effective rock surface rainfall catchment area (ARS). When RI or RA exceeds the critical threshold, the surface runoff with mechanisms of excess infiltration or excess saturation is generated around bedrock outcrops. The discriminating equation will help increase surface runoff prediction accuracy in rocky desertified areas with exposed bedrock outcrops. These results help understand the importance and role of rock surface flow hydrologic processes in karst areas.