Anti-Stall Knobs

AAO Frame

Our AAO (Advanced Acoustic Optimisation) frames feature integrated anti-vibration pads as well as our proprietary Stepped Inlet Design and Inner Surface Microstructures, both of which further refine the fan’s performance/noise efficiency.

Anti-Stall Knobs

The NF-S12A’s Anti-Stall Knobs reduce flow separation phenomena in medium to high impedance situations and thereby increase the fan’s stall margin. This means that the NF-S12A is even more versatile than its renowned predecessor and can achieve better performance on heatsinks and radiators.

Bevelled Blade Tips

Reducing critical rotor stator interaction, the NF-S12B's and NF-B9's Bevelled Blade Tips permit to combine a higher blade surface area with quieter operation and thus form a cornerstone of the fans' outstanding efficiency.

Flow Acceleration Channels

By speeding up the airflow at the crucial outer blade regions, Flow Acceleration Channels reduce suction side flow separation and thus lead to better efficiency and lower vortex noise.

Focused Flow™ Frame

Designed for pressure demanding applications such as heatsinks and radiators, the Focused Flow™ frame features eleven stator guide vanes that straighten, channel and focus the airflow, which allows the NF-F12 to rival the performance of conventional fans running at much faster speeds.

Inner Surface Microstructures

With the tips of the fan blades ploughing through the boundary layer created by the Inner Surface Microstructures, flow separation from the suction side of the blades is significantly suppressed, which results in reduced blade passing noise and improved airflow and pressure efficiency.

Metal bearing shell

In order to guarantee the highest possible degree of manufacturing precision, minimum tolerance and excellent long-term stability, our newest 120 and 140mm fans sport a CNC milled bearing shell made entirely from brass.

Custom-designed PWM IC with SCD

Our custom-designed NE-FD1 PWM IC integrates our Smooth Commutation Drive (SCD) technology. By providing smoother torque impulses, SCD suppresses PWM switching noises and thus makes the fan quieter at low speeds.

Smooth Commutation Drive

The latest version of our advanced Smooth Commutation Drive system ensures superb running smoothness by eliminating torque variations and switching noises. This makes our fans remarkably quiet even at very close distances.

SSO-Bearing

Combining the proven concept of hydrodynamic bearing with an additional magnet that supports the self-stabilisation of the rotor axis, our time-tested SSO-Bearing technology has become synonymous with supremely quiet operation and exceptional long-term stability.

SSO2 Bearing

SSO2 is the further optimised second generation of our renowned, time-tested SSO bearing. With SSO2, the rear magnet is placed closer to the axis to provide even better stabilisation, precision and durability.

Stepped Inlet Design

Our Stepped Inlet Design adds turbulence to the influx in order to facilitate the transition from laminar flow to turbulent flow, which reduces tonal intake noise, improves flow attachment and increases suction capacity, especially in space restricted environments.

Vortex-Control Notches

Vortex-Control Notches split up trailing edge vortices and thus spread the fan’s noise emission over a wider range of frequencies. This measure makes the fan sound more pleasant to the human ear.

Sterrox® liquid-crystal polymer (LCP)

Noctua’s novel Sterrox® liquid-crystal polymer (LCP) compound features extreme tensile strength, an exceptionally low thermal expansion coefficient and dampening characteristics that are ideal for reducing resonance and vibration phenomena in advanced fan-blade designs.

Anti-Stall Knobs

Noctua’s S12 series impellers use a high angle of attack in order to achieve superior airflow. However, impellers with high angles of attack are typically more prone to undesired stall and flow separation phenomena that can occur when the fan is working against higher impedance such as when blowing through tight fan filters or when used on heatsinks and radiators. In these situations when the fan is building up high pressure but less air is moving through, the speed of the air particles flowing alongside the suction side of the fan blades gradually decreases towards the trailing edge. The lower the speed and the higher the counter-pressure, the higher the risk of the air particles becoming detached from the blade surface. This flow separation phenomenon known as stall leads to undesired turbulence, reduced efficiency and translates into a dent in the fan’s performance curve.

The NF-S12A features Anti-Stall Knobs close to the trailing edges of the fan blades. By speeding up the air at this critical point of the blade profile, the Anti-Stall Knobs reduce the risk of undesired stall and flow separation phenomena. This means that the NF-S12A works more efficient than its predecessors in most mid- to high impedance situations despite its slightly lower maximum pressure: While providing a bit less static pressure at the shut off point, the NF-S12A produces more pressure throughout most of the curve, making it better suited for all-round use, tight air filters or even heatsinks and radiators:

Comparing the NF-S12A’s performance curve to its predecessor’s, the improved stall margin is immediately visible: Thanks to the suppression of the stall effect, the dent in the curve occurs much later and less pronounced than with the NF-S12B. Combined with its higher maximum airflow in free flow and further reduced noise emission, this allows the NF-S12A to achieve even better results than its renowned predecessor.